TeacherCandidateFieldworkExperience SchoolReference

In the domain entity TeacherCandidateFieldworkExperience, change SchoolReference from 1..1 to 1..0 so it is unbounded.  This will also require removing SchoolId from the primary key in the TeacherCandidateFieldworkExperience table.  

This needs to be done most immediately in the 3.04 version for UTGV but will also need to be included in the 3.05 version when SHSU and the other US PREP Universities start using the TK20 API.