Changed the way the messages are handled: The editor can now decide what to write in the invitation messages and also include links to the person sending the message and the event the invitation was for. To add links the editor adds [User] and/or [EventName] tags to the message.
Saved the messageText as a complete string in database like the messageTitle with, but now renders as a MVCHtmlString that replaces the tags that the editor may have added with the correct username and eventTitle as a link.

Fixed minor CSS/Html-structure.