Fix #59: Desktop icon install rules
Implement #57: Shortcut to "reset" all the highlights and badges

The defualt value is Ctrl/Cmd+R
Never highlight the badge of a selected item (looks odd)
Implement #55: Settings: view sorting
SessionTreeItem: use ViewInfo::Type for faster sorting
Implement #54: Settings: re-open/remember channels/queries
UserModel: use IrcNamesMessage
Added quassel submodule
WIP: quassel support
WIP: adjusting to the latest quassel source..