Improve nginx configurations. Add HSTS (HTTP Strict Transport Security) support.

git-svn-id: http://svn.code.sf.net/p/openmediavault/code/trunk@1073 3c3d7b80-5828-415e-9f61-280b98178fff
Improve nginx configurations. Add CSP and other additional headers.

git-svn-id: http://svn.code.sf.net/p/openmediavault/code/trunk@1074 3c3d7b80-5828-415e-9f61-280b98178fff