it-lab/grade#29 (comment 111)

*move selector to the center of navbar
*modify link to the selector
*add font icon

* Integration of drag-drop zone
* Some examples about new file structure

* Integration of drag-drop zone
* Some examples about new file structure

Server had been returning number of affected rows minus one: either 0, or -1. This value is converted to bool (res == 0), and js displayed an error.

`Igor Strebezhev` & `Strebezhev Igor` returns the same result

* Renamed AdmStudents -> Students
* New func Students::search()