Improve start up to meeting time

[so010]

This is about testing and startup mirror screen:

• replace remote mirror screen by local mirror screen
• move turn server testing to background
  • update a ICE server list dynamically
  • each peerconnection object should decide independantly if it should restart ICE-machine with new alternative ICE servers from the list
• start up peerconnection as soon as possible (Without TURN-server at all or wait for minimum 1 working TURN-server from iceServerManager?)

[misi]

• Skip ICE protocol/transport combination that are well known that won't work because lack of implementation on Browser side.