Fix duplicate tab detection

Internet Explorer 10 being the only browser that implements the standard correctly.
Add UnbanCommand
Use ViewableMessageList in ChatPage
Remove obsolete Room::getCache()
Join rooms via JavaScript (so JS errors don't lead to a join)

Closes #19
Satisfy CodeSniff
Fix RestoreCommand
Fix userlink in sidebar
Fix hiding of topic when empty
Add InviteCommand
Merge branch 'master' into flexBox