Add a functional test to detect the late hangup bug
Fix grey block flashing on conversation window open
Chat: attach unique ids to calls

This allow us to differentiate calls and drop messages aimed to past calls.
Fix tests
Payloads: Offer carries a callid
More frontend tests
Fix minor typo
Merge pull request #290 from tOkeshu/fix-late-hangup

Fix late hangup
Merge pull request #289 from dmose/flashing-block-fix

Fix grey block flashing on conversation window open, r=@Standard8