Prepare for React 16.

The implementation of ToolbarButtonWithDialog expects a
constructor function for now, not the object returned
from calling a constructor function.

* ref(connection-stats): use PropTypes package

* feat(connection-stats): display a summary of the connection quality

* feat(connection-indicator): show empty bars for interrupted connection

* feat(connection-indicator): change background color based on status

* feat(connection-indicator): implement automatic hiding on good connection

* fix(connection-indicator): explicitly set font size

Currently non-react code will set an icon size on ConnectionIndicator.
This doesn't work on initial call join in vertical filmstrip after
some changes to support hiding the indicator. The chosen fix is
passing in the icon size to mirror what would happe with full
filmstrip reactification.

* ref(connection-stats): rename statuses

* feat(connection-indicator): make hiding behavior configurable

The original implementation made the auto hiding of the indicator
configured in interfaceConfig.

* fix(connection-indicator): readd class expected by torture tests

* fix(connection-indicator): change connection quality display styling

Bold the connection summary in the stats popover so it stands out.
Change the summaries so there are only three--strong, nonoptimal,
poor.

* fix(connection-indicator): gray background on lost connection

* feat(icons): add new gsm bars icon

* feat(connection-indicator): use new 3-bar icon

* ref(icons): remove icon-connection and icon-connection-lost

Both have been replaced by icon-gsm-bars so they are not
being referenced anymore. Mobile looks to have connect-lost
as a separate icon in font-icons/jitsi.json.

Gradually, we exploded the error of CONNECTION_FAILED in multiple
redux state properties. The explosion makes maintenance harder because
the properties have to be updated in sync. Collect them in an object
resembling an Error instance.

Do not show the 'Password is incorrect' message when the LoginDialog
opens for the first time.

It is required to clear the flag, before the connection attempt.
Otherwise the app may confuse deployments without guest access with
a one with guess access if it was visited previously and
the WaitForOwnerDialog was canceled. That's because there will be no
conference related event that clears the flag.

* Implement disabling buttons (like Web had the ability).
* Use consistent colors (e.g. for the buttons) like the rest of the app
  (e.g. WelcomePage).
* Enable AbstractDialog to await a thenable from onSubmit and Dialog to
  render a LoadingIndicator in place of the OK/submit button text.

* feat(AddPeopleDialog): invite rooms

Distinguish between 'user' and 'videosipgw' search result items and
invite them with using different method.

* squash: fix typo in AddPeopleDialog.web.js

It will replace the "Join" text button while appNavigate lasts.

Note about the implementation: when appNavigate completes the component
may have been unmounted and thus we cannot touch its state. In order to
avoid this problem I added a 'mounted' instance variable which gets set
and reset in componentWillMount / Unmount respectively. This is to avoid
using isMounted, which is highly discouraged.

The basic indicator is extracted into a LoadingIndicator component,
which then NetworkActivityIndicator displays (or not) based on network
activity.

In order to support XMPP authentication, we'll need the message
accompanying the error and carried by lib-jitsi-meet's
CONFERENCE_FAILED in the redux store. We already carry the message in
the redux action and we've got the error in the redux store.

In order to accommodate the requirements of the work on supporting XMPP
authentication on mobile/react-native, make dealing with Dialog a
little more generic and a little easier.

Filmstrip only mode displays a device selection dialog that
does not have access to the redux/connect. However, the current
VideoTrack extends from AbstractVideoTrack, which assumes a
redux connection. The fix is to move video display logic into
a separate component and have device selection use that, while
the existing VideoTrack remains connected to redux but
uses the new video display component.

Instead of going through the Avatar object, call the getAvatarURL
directly so that the code flows consistently use the participant
representation within redux.

In certain scenarios we do need to import files instead of features but
even then it is our coding style to not write the file extension.

We broke external_api.min.js by importing react/features/util which
imported react/features/base/lib-jitsi-meet.

1. To reduce the risks of such a breakage until we add
   external_api.min.js to the torture tests, import as little as
   possible in modules/API/external/external_api.js.
2. Use the global JitsiMeetJS on Web in react/features/base/util.