conference: fix current protocol issues

This patch fix 3 little issues:
+ "device" was always empty. Uses the transport to fill the device
field. This will be used in the next version of the protocol.
+ raiseHand was bugguy in two ways:
    + It was only usable by moderators
    + Somebody was able to change the raiseHand for other peers

Change-Id: I32bf37c5063973a5a5962dd8984c87fb05d33a3d