Adminpanel added

# Description
__Adminpanel__ added to GitList, that users of GitList can __add repository-directories__ and make __config-changes__ without editing the config.ini. 

The adminpanel reads all config.ini properties and displays the most important properties. The login data for the admin-panel can be edited in the config.ini-File. Default login data for the admin panel:

 ```
username: admin
password: admin
 ```

# Screenshots
Here are some screenshots of the admin panel.
## Navigation with "Admin"-Button
![1](https://f.cloud.github.com/assets/1528623/993251/0b283428-0996-11e3-8dd0-330ee0934bf9.png)

## Login-Form
![2](https://f.cloud.github.com/assets/1528623/993252/0b3c39aa-0996-11e3-9b44-8300628efe40.png)

## Admin-Panel
![3](https://f.cloud.github.com/assets/1528623/993253/0b4eb080-0996-11e3-8851-12f58057fd52.png)