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

Fixes random tests failures after frameworks upgrade.

* exclude fec-fr secondary ssrcs when looking for primary ssrcs

this was causing us to generate an rtx ssrc for the fec stream

* fix variable

With p2p, inactive lines in the sdp should not be
ignored. Inactive is used to suspend video transfer
to the bridge when dropping back to p2p mode.

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.

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

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