WIP Enrollment API -- Merge to Reg-Login Form branch only

@wedaly @AlasdairSwan @dianakhuang @rlucioni 

Changing the scope of this PR to get the bare-bones requirements in for the Registration and Login changes. This PR will be followed by extensive testing, comments, and general clean up. 

@ormsbee @rocha This will be much more fleshed out with additional stories to address your comments