After taking a new password, the button `change password` always comes `change login`.

- Login filtering
- Complex enter key behaviour
- Process loading icon

Client js tried to get (incorrectly) discipline id from URL and got error at the server side.

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