Branch new-chat-fixes-1

[cemunoz]

This branch is the first one of the 2 existing branches for the chat plugin. The other (new-chat-logs) is created from this one and includes all the stuff referred to the logs, as well as some other improvements that will be named in its ticket.

new-chat-fixes-1 features:

-The screens for administrators, the conference management part referred to the chat, and also the conference display (also meeting and lectures).

-Components have a priority attribute. This is quite useful if you want to make sure that, given an event, some of the components subscribed are executed before others.

-Notifications are sent when creating, editing or deleting a chat room.

-First version of the Join Now! links. They don't feature custom links, though.

-Chat room cloning.

-How to connect message is editable in the administration part thanks to a ckEditor.

-RHMap with the stuff for WSGI.

-Adapted to sleekxmpp 1.0.

-Use of ExternalOperation? for sending emails in notifications.

-ContextManager? is used in the MailHelper? to make sure that emails are sent only once.