Remove vigil functionality

[bbmcmann]

The site no longer uses vigils, instead shifts will be stored in one large shifts collection. Users will not have a list of their own shifts.
Need to go through the signup functionality and remove all db operations that use vigils and the vigil shifts collection, then replace these with the new schema(see below).

1. When a user signs up for a shift, the shift should be pushed to the new "shifts" collection in the database.
2. The calendar should pull shifts from the new shifts collection in the db instead of each vigil.