added ChatDB to all instances
sendMessage with chatDB in all files
changes to ChatDB
mutex
added empty set functionality
added callbacks
fixed Problems in common
Fixed server/
fixed server/...again ;)
moved InterSErverImpl and fixed it
initChat, leaveChat now work with ChatDB; IceServer, local exported
small changes to username
Merge pull request #20 from sepm-depm/ServerMR

Server mr