Adds a flag which can be used to disable talking to Jicofo. It's
intended to be used only in jitsi-meet-spot which joins a special room.

In order to include browser capabilities in RTCBrowserType I needed to
refactor RTCBrowserType.

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.

Because the implementation of LocalStorage in jitsi-meet at the time
of this writing is asynchronous with respect to loading and saving,
delay the generation of machineId in order to allow LocalStorage to
load any previously saved value.

Currently Jicofo does not include 'session-invalid' tag when there is
"machine ID" and "session ID" mismatch, but in such case the session-id
must be cleared as well. Otherwise we'll end up in an endless loop.

With JitsiAuthConnection the API consumer has to:
1. JitsiConference.createAuthenticationConnection,
2. JitsiAuthConnecition.authenticateAndUpgradeRole,
3. Wait on the Promise of 2,
4. Maybe cancel the JitsiAuthConnection of 1.

With authenticateAndUpgradeRole the API consumer has to:
1. JitsiConference.authenticateAndUpgradeRole,
2. Wait on the thenableWithCancel of 1.
3. Maybe cancel the thenableWithCancel of 1.

Some browsers may not support data channels (hi there, Edge!) and sometimes it
may not be desirable for other reasons.

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

Make no assumptions about the default value in Jicofo.

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

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

* 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

Because the flag is required in the connection options anyway it will
be better to use it from one options set only to avoid redundancy.