HTML5 client: new sliding menu.

 - implement message handlers

Fixed the issue with the screen not darkening after opening one of the menus while the other one is open.

Disabled the sample poll display

First pass of poll visualization

Polling partial implementation

 - start implement poll message handlers in meeting actor

Fix welcome message and private chat bugs

 - fix private chat bug
 - start implementing polling

Merge branch 'development' of https://github.com/bigbluebutton/bigbluebutton into implement-polling-v3

HTML5 chat fix + logs ignoring

Merge branch 'master' of https://github.com/bigbluebutton/bigbluebutton into merge-with-akka-fs-and-akk-apps

HTML5 client: raise/lower hand.

Correctly positioned the whiteboard buttons and made the Raise/Lower Hand button hidden in fullscreen mode.