When upgrading a call, offer to accept or ignore the call.
Add ignore for upgrading calls, and adjust outgoing calls to not start the timer before gUM is finished.
Handle no peer connection being set up when terminating a window, e.g. in the case of no call established, but the call initiation being timed out.
Merge pull request #158 from Standard8/upgrade_offer

Add accept/ignore option for upgrading calls, and add a timeout