Remove Datatree branch_find decorator

The logic has been moved into the QSD view, which is in my opinion the
only place it belongs.
Remove unused miniblog decorator/view code and QSD template
Fix edit link on QSD pages
Remove extra cls.teachers() reference
Remove unused cronmail code that referenced Datatree/Userbit
Remove unneeded class_transition.py
Add Program.program_type property - returns e.g. 'Splash'
Add Program.program_instance property - returns e.g. '2013_Fall'
Update class reg controller to stop using Datatree

There were some references to the class's anchor, as well as some
Datatree-specific stuff (like re-assigning teachers whenever the e-mail
code changed) that we don't need anymore.
Update Datatree references in class reg controller e-mails

Makes use of the program_type and program_instance properties recently
added to Program, as a substitute for looking up the anchor and parent
anchor names.
Update Datatree references in lottery controller Mailman calls
Remove Datatree reference in lunch constraint generator
Fix Datatree reference in places where Events are saved
Remove unused has_edit variable in render_qsd template tag
Fix Permission typo in ajax_qsd view - thanks Anthony