* ref(TraceablePeerConnection): rename var to what it is

* ref(ssrc info): get rid of 'ssrc' and 'group' roots

Removes 'ssrc' and 'group' root Objects from "ssrc info" structure.
Also removed redundant 'primarySSRC' from the group.
Do not split and join back and forth the SSRCs, but store them as
numbers.

* feat: add SdpTransformUtil

* ref(rtxModifier): rename "previousAssociatedRtxStream"

* ref(RtxModifier): use for .. of

* fix(SdpConsistency): organize imports

* fix(RtxModifier): organize imports

* ref(JitsiLocalTrack): simplify the expression

* extract MLineWrap (ongoing)

* ref(TPC.extractSSRCMap): some ES6 cleanup

* ref(RtxModifier): use template strings

* doc(SdpTransformUtil): update and fill missing

* ref(SdpTransformUtil): const, template strings

* style(TPC): object formatting

* ref(JitsiLocalTrack): simplify expression + syntax

* ref(TPC): more "extractSSRCMap" improvements

* ref(RtxModifier): const all the things

* ref(SdpConsistency): template strings

* ref(SdpTransformUtil): syntax + other

* doc(SdpConsistency): add throws description

* fix(TPC): broken "extractSSCMap"

* fix(JitsiConference): adopt to Map

* ref(SdpTransformUtil): remove forEachSSRCGroup and static methods

necessarily handle the translation of groups correctly)

* 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