first approach to ywam_references
create a many to many polymorphic relation betwee fieldhost/student and reference through person_reference class
Fix creation of references on student application form.

"blank" reference forms were not being properly excluded in the student
application form after the internal relationships were refactored to
many-to-many.

The student application attributes were being setted twice, causing
person references to be duplicated.
Fix javascript validations for students/setup after refactoring References
Add javascript validations in projects/setup for YAWM references after refactoring References model.
Improve PersonReferences and References features in project/setup and student/setup
Integrate person_references and references refactor in students/setup with SF