screenshare/html5: rewrite most of the client side code

Added new SFU broker for screen sharing

Removed kurento-extension entirely

Added inbound and outbound reconnection procedures

Improve UI responsiveness when sharing

Add reconnection UI states

Redo error handling

Refactor actions-bar screen share components. Make it smarter with less prop drilling and less re-rendering. Also more readable. Still work to do in that I think

Add a connection retry procedure for screen presenters when they are sharing; try a configurable amount of times when failure is triggered, with configurable min and max reconn timeouts and timeout increase factor

Make local preview attachment smarter

ADD PARTIAL SUPPORT FOR AUDIO SHARING VIA SCREEN SHARING WITH GET DISPLAY MEDIA, RECORDING STILL NOT SUPPORTED!!!