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

Minimized JS should not be included, since it can't be modified.
Instead, a script should be given to minify (or compile) source at first launch.