Fixed bug so that when adding/updating content to a cohort, if the tree lists the same course multiple (in two or more different cohorts) only the first occurrence of the course will allow the professor to add or remove content from a 'professor' type menu item.

Cleaned up some of the code to more closely follow elgg best practices.

As far as I can tell, the current code base is bug-free.  Need to continue cleaning up the code before moving forward with additional functionality.
Minor fixes