Secure headers, reduce static content size

- This pr is about reducing size of the stuff that gets loaded, like images/css/js etc and to make htpc manager a little more secure against xss attacks. 
- Auth is disabled for all static content.
- Remove some unneeded code

Closes https://github.com/styxit/HTPC-Manager/issues/272

This is just to clean up some of the issues that should be closed:
Closes https://github.com/styxit/HTPC-Manager/issues/279
Closes https://github.com/styxit/HTPC-Manager/issues/284
Closes https://github.com/styxit/HTPC-Manager/issues/236
Closes https://github.com/styxit/HTPC-Manager/issues/235
Closes https://github.com/styxit/HTPC-Manager/issues/171
Closes https://github.com/styxit/HTPC-Manager/issues/166
Closes https://github.com/styxit/HTPC-Manager/issues/162
Closes https://github.com/styxit/HTPC-Manager/issues/144 i cant find any ref to the missing image in the code now
Closes https://github.com/styxit/HTPC-Manager/issues/126 Works fine now
Closes https://github.com/styxit/HTPC-Manager/issues/122

Just because of their license. GPL enforces the fact that you should be able to modify them.
Yes, it's the open-source thing. But usually, a simple Makefile with a call to a minifier should do the trick