Usage: $this->user->Faculty->ID or $this->user->Faculty->getDisciplines()

* Moved some static methods to Factory model
* Removed unused param $teacherID
* Assertion checks moved to models

Use RusLang::tr() function instead.

Field Model_Factory::ID came public, new method getStudents() added.
Renamed Model_Students::searchStudents() to search(); removed duplicate method NotAttendingDiscipline().

1) fix Rating Model
2) sql CreateSubject: restore expected behavior (see todo in commit "Refactoring of subjects upload page" 19.06.15)
3) refactor and disable JavaAuth (see todo)

Not all servers detect HTTP_X_REQUESTED_WITH header.
And now it is possible to load excel files.

Default faculty was not defined by default.

Russian constants are moved to twig & RusLang modules.
Functions were renamed to Semesters::load($id) & Semesters::loadAll().

Moved some functions from Account to Model_Account & Model_Teacher.