Refactors the previous "[RN] Cache avatars and provide a default in
case load fails" for the purposes of simplification but also modifies
its functionality at the same time. For example:

- Always displays the default avatar immediately which may be seen if
  the remote avatar needs to be downloaded.
- Does not use random colors.
- Uses a default avatar image which is not transparent and ugly but at
  least it's the same image that's used on Web. I've started talks to
  have images/avatar2.png replaced with a transparent and beautiful
  so that will land later on and we'll see the automagic colors in all
  their glory then.

Avatars are cached to the filesystem and loaded from there when requested again.
The cache is cleaned after a conference ends and on application startup
(defensive move).

In addition, implement a fully local avatar system, which is used as a fallback
when loading a remote avatar fails. It can also be forced using a prop.

The fully local avatars use a user icon as a mask and apply a background color
qhich is picked by hashing the URI passed to the avatar. If no URI is passed a
random color is chosen.

A grace period of 1 second is also implemented so a default local avatar will be
rendered if an Avatar component is mounted but has no URI. If a URI is specified
later on, it will be loaded and displayed. In case loading the remote avatar
fails, the locally generated one will be used.

feat(device-errors): move device error dialogs to notifications

- Create a notification component for displaying a toggle.
- Create an action for showing the component if allowed by
  the local storage setting and for saving the setting to
  local storage.
- Remove all notifications having a timeout by default so the
  device error notification must be dismissed manually.
- Split the camera and mic error dialog into two separate
  notifications.

doc(iframe_api): Fix the names of the properties in the options object.

* feat(presence): display status in thumbnail and large video

- Create a React Component for displaying presence. It currently
  connects to the store for participant updates but in the future
  should not be as smart once more reactification occurs.
- Modify filmstrip css so the presence status displays horizontal
  center and below the avatar.
- Modify videolayout css so the presence status displays horizontal
  centered and with a rounded background.
- Dispatch presence updates so the participant state can be update.
- Update message position on large video update to ensure message
  positioning is correct.

* squash: do not show presence message if connection message is displayed

Hides the UI component showing dialout codes and uses the dial input without validating it.

Skips printing error when dial-in numbers is not configured.

- Swap the telephone input with FieldText.
- Swap the dropdown trigger input with FieldText for styling
  consistency with the telephone input.
- Wrap the dropdown trigger so it can be modified with jitsi css.
- Use flexbox to have the trigger and input align horizontally
  but have the input take up width if the trigger is not displayed.

* feat(notifications): implement a react/redux notification system

* squash into impl explicit timeout, style

* ref(notifications): convert toastr notifications to use react

* ref(toastr): remove library

* squash into conversion: pass timeout

* squash into clean remove from debian patch

Apply the same early audio muted logic as for the video.

Make toolbar's microphone button enabled whenever there are any
'audioinput' devices available and allow to add audio during
the conference even if microphone permissions were denied on startup.

In iOS this is automagically done in the view destructor, bunt we don't have
that luxury in Java we have to do it manually.

The new disponse() method MUST be called when the Activity holding the view is
going to be destroyed, typically in the onDestroy() handler.

Whatever I've tried so far ends up failing in really weird ways, so let's admit
defeat, for now. Destroy containers only on Android.

This shall be revisited when we update RN to version >= 0.43 and we have
"display: 'none'" available.

We must not pass nil as the URL, that will translate to null and we won't be
able to load the initial URL which is passed as the launch parameters.

Web's ExternalAPI accepts an object with properties as one of its
constructor arguments and from which it generated a URL. Mobile's
JitsiMeetView.loadURLObject is supposed to accept pretty much the same
object.

Our fixes have been applied upstream and a release has been made.

NSDictionary doesn't support nil values, they must be objects, so use NSNull
instead, which is the kosher way to do it.

Introduces loadURLObject in JitsiMeetView on Android and iOS which
accepts a Bundle and NSDictionary, respectively, similar in structure to
the JS object accepted by the constructor of Web's ExternalAPI. At this
time, only the property url of the bundle/dictionary is supported.
However, it allows the public API of loadURLObject to be consumed. The
property url will be made optional in the future and other properties
will be supported from which a URL will be constructed.

Initializing a new URL/NSURL instance is a chore especially when one
takes into account that the JavaScript side (1) is loading the URL
asynchronously and (2) is capable of parsing strings that may or may not
be represented as URL/NSURL.

The Android method loadURLString(String) may have been called
loadURL(String) to overload loadURL(URL) but I didn't want to do that
because:

1. It would not be compatible with existing source code such as
loadURL(null) which would have become ambiguous.

2. I wanted to achieve better convergence with the iOS API.

When a Container is not visible there is no need for it to react to touch
events, thus avoid wrapping it in a touch component.

In addition, simplify the style needed for hiding the component. Moving the view
out of the window boundaries no longer works on RN 0.42 on iOS. Seting the size
to 0 works well on both platforms, but in the future (when we upgrade to RN >=
0.43) we should switch to display: none:
4d69f4b2d1

fix(AudioOnly+web): crash when untoggle audio only

Because on web video track is stored both in redux and in 'localVideo'
field, video is attempted to be unmuted twice when turning off the audio
only mode. This will crash the app with 'unmute operation is already in
progress'. This commit will prevent from taking action from the web
world if the video track already exists and will make the redux side
rollback unmuted status in case unmute fails.

In another installment of "how on earth?!", using a 1px border instead of a
0.2px border fixes view clipping on a device where it didn't work before
(Moto X Play).

Observations:

- When nothing was rendered, rotating the device made the buttons show up, this
  makes me think the Surface is not properly composited with the toolbar view
  for some reason. Why this happens in some devices and not in others remains a
  mistery.

Other approaches attempted:

- Setting View.collapsed to false so it will remain in the view hierarchy. It
  made no effect.

- Setting View.needsOffscreenAlphaCompositing to true. It made no effect.

Just like before, I came up with this workaround by accident, but couldn't find
another way, so here we go again.