Change Admin-Username in Setup and Configuration

[HDValentin]

Baikal version: 0.9.x

Problem you are having:
The Username of the Administrator is 'admin'. The possibility to change the username to something individual would make the backend more secure. The username is then probably no more guessable. For example Claus235424ab. The attacker script needs then two components: username and password.

Suggested solution:
Possibility to change the admin-username in Backend.
Possibility to change the admin-username on installation.