Also add MucConfigFormManager and improve the MUC API (SMACK-648). Bump
to jxmpp 0.5.0-alpha3.
Improve and extend PrivateDataManager and BookmarkManager.
apply the Manager pattern to 'muc'. This prevents the user creating
multiple MultiUserChat instances for the same MUC.
Move the static method from MultiUserChat to MultiUserChatManager.
Also add AbstractNodeInformationProvider.