Middlewares should not be loaded on mobile as there is no way to use the
functionality.

* Integrate rtcstats

* expcetion handling / clean up

* order imports

* config fix

* remove mock amplitude handler

* additional comments

* lint fix

* address code review

* move rtcstats middleware

* link to jitsi rtcstats package

* address code review

* address code review / add ws onclose handler

* add display name / bump rtcstats version

* resolve import error

Also, use the configured resolution to set it as the max received frame size.

Up until now we relied on implicit loading of middlewares and reducers, through
having imports in each feature's index.js.

This leads to many complex import cycles which result in (sometimes) hard to fix
bugs in addition to (often) breaking mobile because a web-only feature gets
imported on mobile too, thanks to the implicit loading.

This PR changes that to make the process explicit. Both middlewares and reducers
are imported in a single place, the app entrypoint. They have been divided into
3 categories: any, web and native, which represent each of the platforms
  respectively.

Ideally no feature should have an index.js exporting actions, action types and
components, but that's a larger ordeal, so this is just the first step in
getting there. In order to both set example and avoid large cycles the app
feature has been refactored to not have an idex.js itself.