* Skips setting undefined device id to sink in audio preview.

* Fallbacks to use labels for user selected devices.

* Fixes comment.

* fix(PresenceLabel): Use translated strings for the presence label.

* feat(sounds): Implements loop and stop functionality.

* feat(invite): Add ringtones.

* fix(invite): Code style issues.

Adds base/sounds feature which allows other features to register a sound
source under specified id. A new SoundsCollection component will then
render corresponding HTMLAudioElement for each such sound. Once "setRef"
callback is called by the HTMLAudioElement, this element will be added
to the Redux store. When that happens sound can be played through the
new 'playSound' action which will call play() method on the stored
HTMLAudioElement instance.

Prepares for the latest eslint & flow-related npm packages which cause
these errors.

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.

Additionally, remove jshint because it's becoming a nuisance with its
lack of understanding of ES2015+.

Prepare for React 16.

Introduce certain React Components which may be used to write
cross-platform source code such as Audio like Web's audio, Container
like Web's div, Text like Web's p, etc.