[Engine-Campfire] Keep better track of the event streams

Keep a chat-stream mapping and dispose the event stream when the chat
is closed to clean up the network connection (closes: #827).
[Build] Silence! I Kill you!
[Engine] ServerModel now sends and receives ValidateServerCertificate and UseEncryption again
[Engine-XMPP] Removed jabber-net2005 and moved to agsXMPP
[Engine-XMPP] Resources and Priorities are now properly supported
[Engine-XMPP] Disable MUC until fully loaded. Open Contactchat on reconnect. Allow custom away messages. Remove outdated comments.
[Engine-XMPP] Can now connect through a proxy
[Engine-XMPP] Refactored Reconnect. It now does a clean reconnect and doesn't crash anymore due to internal socket stuff.
[Engine-XMPP] enabled parsing of html messages
[Engine-XMPP] display error messages in their appropriate chat tab if such a tab exists. else display in protocolchat
[Engine-XMPP] print chatstates in private chats
[Engine-(XMPP|IRC), Frontend-GNOME-(XMPP|IRC)] Moved StarkSoftProxy from SmartIrc4net into its own project
[Engine-XMPP] Fix contactlist for contacts that are not in the roster

when a contact who is not in the roster sends presence packages, this can cause error messages because the state of the contact was thrown away.
[Engine-XMPP] added whois command to display xmpp specific information
[Engine-XMPP] Refactored join command
[Engine-XMPP] created invite command

note, this is only delegated invite, direct invite is not supported by agsxmpp
[Engine-XMPP] added "addgroup" command to add a contact to a roster group
[Engine-XMPP] Show message when invited to a muc

Note: the generated join-hyperlink is not supported by smuxi yet
[Engine-XMPP] fix adding contacts to roster for some servers

some servers don't follow the standard properly, they only properly support subscribing to/from contacts that are in the roster
[Frontend-GNOME-XMPP] specialize PersonChatView for xmpp