Fire CONFERENCE_LEFT event after conference is left

Fix JitsiLocalTrack dispose() method

Handle case when JitsiLocalTrack#dispose() is called after track was removed from conference.
Set track's conference reference to null when removing track from conference.

Implements audio problems detection

Expose JitsiTrackError through JitsiMeetJS.errorTypes.JitsiTrackError

Removes getVideoId and getVideoSrc as no longer used by tests.

Be forgiving towards API clients

If the API client happened to try to add one and the same local video
track twice, the library would throw an error. I find that draconian
because:

1. The error message states that a second local video stream cannot be
added but that is incorrect because the API client is not trying to add
a second local video stream but add one and the same local video stream
multiple times.

2. The jsdoc says that a throw will happen if another local video stream
is added but that is misleading because the API client is not trying to
add another local video stream but add the same local video stream.

3. Adding one and the same local video stream multiple times can be
handled gracefully by the lib-jitsi-meet library. Thus, the library
appears more friendly.

Hence, gracefully handle the case of adding the same local video track
multiple times without throwing an error.

Fix logging audio output device to callstats

Fix non-ASCII letter in Statistics.sendActiveDeviceListEvent() method

Fixes JS error on desktop streaming start

Adds additional check, avoids undefined error.

Needs an additional check for available devices after merging https://github.com/jitsi/lib-jitsi-meet/pull/139.

Logs active devices to callstats (updated).

Call addNewFabric only if callstats is initialized, there are certain situations when the init callback for some reason is slow and we call addNewFabric before callstats is initialized and we skip the peerconnection reported so we are missing the stats. Reports data only if callstats had initialized, adds caching of associateMstWithUserID calls.

Fire an optional JitsiMediaDevices.PERMISSION_PROMPT_IS_SHOWN event when JitsiMeetJS.createLocalTracks()

Don't fire RTCEvents.DEVICE_LIST_CHANGED for the first time we get devices from enumerateDevices()

Raise hand2

Bumps sdp-simulcast version.

Bumps the sdp-simulcast version to 0.1.7 that fixes issues related to SSRC
management.

Don't mix old and new-style for gUM constraints for Chrome, as it fails with TypeError in new Chrome versions

Fixes issue with the local audio levels

Fix error when no global JitsiMeetJS var is available

Ignore "bridgeIsDown" presence from non-focus members.

via presence (via special items with a tag name beginning with
"jitsi_participant_). An events is fired when the value of a property changes.

Refactor callstats removing improve static calls to Statistics.