Tasha fixes

This pull request entails changes made in my previous pull request and modifications/ additions I have started making since 4/4 meeting with tasha. 
The most prominent additions include eligible_teams and eligible_students. furthermore, I added coach field and active columns to students/teams. I then began working on destroying a student, but have not successfuly create a callback for deactivating a registration when deactivating a student.

UPDATE: OK, this pull request got kind of massive. Most of the additions are noted below in the form of commits, but the important take away is that now, all creation, movement, and deletion of data from the user perspective is fully functional (not fully tested). Certain actions have been modified to prevent to prevent loss of data, and certain other actions have been hidden from the user view because they are critical for the full registration, but work poorly alone. Additionally, options for creating/movement of data has been limited to only the applicable objects in places like adding students to a team, creating a team, etc. A lot of the features here were used to justify the closing of multiple issues that can be viewed in Shaun's repo.