Rework semester DB field and separate data from display
It's the frontend's job to display the value as a nice user-friendly manner -- the database backend should only store short concise values that don't have strings in them and are case-insensitive.
The MR makes the DB store "none", "sem1", "sem2", "full" as the semester field instead of "--", "None", "Semester1", "Semester2" and "FullYear".
Includes a migration to change the database field's choices attribute.
(As a side note I think we should remove the Semester field entirely, it's useless in practice because DRPS and Learn and Path exist, and it's a hassle for admins to set it correctly)