Screenshare sound and lock fixes

Only use chromeExtensionLinkURL if it is set

V2.0.x release ui fixes

Improve bigbluebutton cleanup cron job

Show layout name as in xml file when its name cannot be matched from locale file

Full screen button is only added on Android

Disable screenshare init for presenters on mobile devices.

- Fully clean up temporary stream files for all red5 webapps.
- Also clean up temporary stream files for kurento recordings.
- Add a new, separate variable for controlling maximum time to keep
  log files.
- Clean up old (rotated) log files for red5, tomcat, recording which
  were accumulating.

HTML5 WebRTC listen only via Kurento/SFU

Also did some refactoring to kurento-extension parameters

Add additional step to installing PPA for ffmpeg

Update hardware acceleration warning style and help page

Improvements to Breakouts on HTML5

 - check if chat message is available to prevent NPEs

Merge branch 'client-type-get-meetings' of https://github.com/antobinary/bigbluebutton into antobinary-client-type-get-meetings

Fix #5725

Bump version to RC1