Add 'CTSO' option to WBL Events as a 'send to' option

Currently there is no way to invite members of a CTSO club to a WBL event. We need to track CTSO meetings and other events and the only way to do so is to create the events under WBL. We currently have to create each CTSO as a student group in order to invite a CTSO to an event. This is an extra step and time consuming especially if members update. It would be nice to have a CTSO option instead.