Fixes #7093.

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.

React Native doesn't define __filename nor __dirname so do it artisanally. In
addition, this helps with centralizing the configuration passed to loggers.

🔥🔥🔥

Using anything non-serializable for action types is discouraged:
https://redux.js.org/faq/actions#actions

In fact, this is the Flow definition for dispatching actions:

declare export type DispatchAPI<A> = (action: A) => A;
declare export type Dispatch<A: { type: $Subtype<string> }> = DispatchAPI<A>;

Note how the `type` field is defined as a subtype of string, which Symbol isn’t.

Since they are a language feature, they make the source code more easily
comprehensible than `if (typeof XXX === 'undefined') { XXX = ...; }`.

- Increase z-index so the subtitles display over tiles.
- Add a background to the subtitle text.
- In general make the subtitles narrower.

* Shows final translated speech to text results as subtitles

* Use conference from redux state and removes addTranscriptMessage

* Show subtitles when Jigasi sends transcription results in JSON

* fix: Import PropTypes from prop-types.

* apply feedback on initial PR

* Changed Object to Map, alphabetic ordering fixes ,css changes in transcription subtitles

* Sends Map of transcriptMessages as prop to Component

* Documentation fixes and uses config in redux state

* Minor doc fix

* rename feature 'transcription' to 'subtitles'

* Moves subtitles config to interfaceConfig and minor fixes

* minor lint fix