#119 Add teacher insertion to API

* Add getDepartmentIdByName API (with auxiliary procedure)
* Add teacher insertion (only one at the time)
* Add token checking to user authorization in API handler
* Add throwing away HTTP exceptions in API handler
* Add functions for throwing HTTP exceptions (403, 404)
* Add singing in by tokens in User
* Add autocompleting department's ID by name
* Add error handling (show 400 bad request, if any require data missed)
* Add batch processing
* Add autocompleting job position ID by name