#74 roles management, change role page, fix both profiles and students search

* Move SetRole and GetRoles to migrations
* Add RoleID to GetFullInfo output
* Fix and refactor controller of roles
* Fix model of roles
* Fix and refactor change role page
* Fix link to teacher's profile
* Add link to change role of the teacher and remove redundant checks in teacher's profile
* Fix search of students
* Fix link to student's profile