add headers

X-Frame-Options	SAMEORIGIN
Pragma	no-cache
Merge branch 'develop' of https://github.com/Edugate/ResourceRegistry into develop
cleaning
cleaning
cleaning
cleaning
fvalidator during registration
start implememnting - #110
exclude empty md:Extensions
Merge branch 'develop' of https://github.com/Edugate/ResourceRegistry into develop
Merge branch 'develop' into 1.x-stable