Protect settings, sexy login, manage users

- Adding htpc username and password enables auth. Digest auth is replaced with a form based one.
- Add and manage users from the manage user module
- Logout button is only visible while logged in 

Users does not have access to to kill processes, use the commandline in stat module, shutdown server and the settings page. Clicks on restricted links will be redirected to the login page. Ajax calls are simply ignored. It might be other this that is restricted but thats what i can remember from the top of my head. 

http://imgur.com/nHbcZhG
http://imgur.com/ftyrr7C
http://imgur.com/954qgsm

https://github.com/styxit/HTPC-Manager/issues/165
https://github.com/styxit/HTPC-Manager/issues/186