Implemented "CreateChannel" in RentItServer.ITU namespace. Not at all sure if it works :]..

Refactored controller, _channelSearch TST is now replaced by _channelCache Dictionary<int, Channel> in order to take some pressure of the database. This dictionary is now checked before any database query when calling "GetChannel(int channelId)"
Moved stuff around in RentItModel.edmx so it looked a bit better :))