* Fixed bug with students search
* Documentation for Model_Student
* Utility function Arr::groupBy()

Simplified methods. If you want to group elements by any key, write ->as_array('key').

Separated logic and representation, removed unused functions, duplicates

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().

– Type constants (exam, credit)
– New function exists()
– More clear method names