Added MucListener

Conflicts:
	src/main/java/de/xsrc/palaver/utils/Utils.java
Moved connection logic to tasks
Move Bookmark Sync to ConnectTask
F:CRUD on account reconnects connections
Use Tasks and Executors

- At the moment for convinience is the ObservableTaskExecutor used, not
  sure if it's a good performance sollution
Fixed Conference Bookmarks
F:Join Bookmarks Bug
ConnectionManager is a proper Singleton now
A:Delete Contacts / Conferences from contactsview
F:Bug in bookmarking mucs
Implements MUC autojoin
F:Conference Removal Bug
Closing Palaver makes conference autojoin = false
Rework MainView