* feat(multi-stream-support) Add the support for multiple local video streams.
This feature is behind 'sendMultipleVideoStreams' config.js flag and is currently supported only on clients running in Unified plan mode.

* squash: Use the track index from source name to find the matching transceiver on unmute.

* fix(sdp): provide SCTP streams, because the XMPP parser expects them

* fixed linting error

This PR switches to generating sctp-port based SDP.
It also adds support for parsing sctp-port, but can handle
fallback to old-style sctpmap as well.
Fixes: #1778

the protocol was switched back in Chrome 44 in 2016:
  https://bugs.chromium.org/p/webrtc/issues/detail?id=2796
the port switch more than five years ago too.

The issue was caused by incorrect ordering of the mixedmslabel mline.
sdp-interop is expecting that this mline was the first one but in
reality we were placing it last. This was causing the direction of a
user related m line to be sendrecv instead of sendonly. In certain
situation this issue was causing 2 MediaStreamTracks associated with a
single MediaStream/participant.

This is the first step in adding support for multiple
streams per endpoint. Each source(stream?) needs to have
an identifier. For now always generate the 0 index name
until the machinery for sending more than 1 stream is put
in place.

* send only MSID attribute

* add feature flag for source name signaling

* log a msg if source name signaling is enabled

This fixes an issue where the bridge doesn't forward the HD stream from Firefox to other users in the call. The order of the ssrcs produced by the browser is from Highest resolution to lowest whereas the bridge assumes it to be from lowest to highest as is the case in Chrome and Safari.

When a msid attribute is missing in the 'a=ssrc' line, use the local endpoint id as an indentifier. Move this generation logic to LocalSdpMunger. Also suppress notifying Jicfo of a ssrc change on Firefox when the change is a result of the media being suspended on the jvb connection.

In certain cases, when RTCPeerconnection#addTrack is used, the browser doesn't produce the streamid in the 'a=msid' line which is being used by Jicofo as a unique identifier for the associated ssrc. Whenever the msid is missing in the local description, generate an ID using the local endpoint id.

SDP utility classes are spread across RTC and XMPP directories now, moving these class files to a 'sdp' directory.

which should include the colon in order not to match something like
  a=simulcast-is-cool

in order to not match a=msid-somethingelse, a=ridiculous and similar

mostly removing the 'tmp' variable. Renaming 'media' to 'sdp'
in some places.

not used elsewhere. Also the common term for this is munging
these days.

using more specific selectors

removes the SDES mapping. This is a leftover of the time when
Chrome only supported SDES and shouldn't be required anymore.

This has become obsolete thanks to ES6 arrow functions

removing an old FIXME

and make the code use arrow functions with named parameters in .each()/.map.

removes two unused methods for mangling SDP.

Co-Authored-By: Saúl Ibarra Corretgé <s@saghul.net>

Use unique session id per TPC.
Translate a=rid to Jingle only when simulcast through RIDs, i.e., ssrc-less simulcast is supported

* fix(migration): reject the data channel to restart it

Starting on chrome 63, an error occurs when renegotiating
with the new bridge on bridge migration when the SDP sections
do not match, which occurs when removing the data channel
section. Not doing the double renegotiate prevents the data
channel from being reopened. The way around this, while still
avoing the error, is to reject the data channel section instead
of removing it to trigger a new data channel.

* squash: reword comments

Ssrcs not grouped together in the jingle element
are not recognized by the bridge. When parsing an
sdp with ssrcs that are not listed consecutively
it is important to still group them together
in the jingle element.

ESLint 4.8.0 discovers a lot of error related to formatting. While I
tried to fix as many of them as possible, a portion of them actually go
against our coding style. In such a case, I've disabled the indent rule
which effectively leaves it as it was before ESLint 4.8.0.

* add support for signaling simulcast for unified plan

1) munge the incoming offer to advertise support for receiving simulcast in unified plan
2) add 3 simulcast encodings via rtp sender
3) inject an ssrc-group line, even when using rids for simulcast (jicofo will rely on this)

* add rid information to the session-accept jingle

* address lenny's feedback

* make firefox simulcast configurable

* fix missing comma

Webpack 2 defines module.exports as a read-only property in ES6 modules.

Webpack 2 defines module.exports as a read-only property in ES6 modules.