Move JingleSessionPC from ChatRoom to JitsiConference

This commit removes dependency on ChatRoom and JingleSessionPC from
the TraceablePeerConnection.

cleanup: remove old adaptive simulcast config option

doc: remove browserify mention from README

cleanup: Renames a function, adds documentation.

feat(lastN): Add ability to dynamically change lasN

The option got axed, there is nothing to handle now.

cleanup: remove adaptive las N config option

The feature has been replaced so the option no longer applies.

if enabled, prefer to use h264 (if it exists in the offer)

add a multi-codec test case for preferCodec

Strip rtx

necessarily handle the translation of groups correctly)

don't add rtx streams on firefox

Some runtimes such as React Native don't have a window.location.protocol
property, so don't check for it, assume removeStream is available.

The configuration of webpack 1 does not fully work on webpack 2 without
modifications.

Unfortunately, webpack 2 produces a larger jitsi-meet bundle at this
time. Since the webpack version of lib-jitsi-meet is restrained by the
webpack version of jitsi-meet, we cannot move to webpack 2 right now.

* re-enable setting for enabling/disabling rtx

* add tests for rtxmodifier.  (and a bugfix found by the tests)

* remove rtx handling from sdp-consistency (it will be handled separately)

* better error printing in JingleSessionPC around renegotiation

* add rtx modifier to handle inserting local rtx ssrcs, keeping local rtx ssrcs consistent, and imploding remote rtx ssrcs

* jsdoc, es6 cleanup, logging tweaks

* fix line that's too long

* add a 'parseGroupSsrcs' helper function

* fix a bug when passing group ssrcs to be parsed

* address pr feedback

* address pr feedback

* fix for loop

* address pr feedback

* better const in SampleSdpStrings

Fix conference being broken after someone without any video device joins (ver 2)

Video SSRC has to be generated for the recvonly stream if there are no
video tracks in the PeerConnection.

Fix crash on screensharing when video muted

cleanup: Make desktop sharing options consistent and drop deprecated …

Make sure there are options to set the extension ID and an enabled flag for
both Chrome and Firefox.

Removed checking for deprecated configuration options: desktopSharing,
chromeExtensionId and minChromeExtVersion.

Fixes crashed when null stream (muted) is being removed.