fix scss and js include paths
Merge pull request #507 from sulu-cmf/bugfix/scss-js-import-paths

[BUGFIX] fix scss and js include paths
fixed codestyle
added _links to collection response, added possibilty to choose url from _links in grid-group
fixed code style
added changelog
Merge pull request #556 from sulu-cmf/bugfix/collection-url

Use hateoas _links to generate urls in grid-group (usage in media-selection)
added security contexts to SuluMediaAdmin
implemented SecurityContext as class because of symfony conventions
added sulu specific security checker
added compiler pass for adding the SecurityChecker, if security is enabled
implemented listener for Sulu specific security
added SecuredControllerInterface for defining requried security context in each controller
added locale to SuluSecurityListener
fixed controllers with new getLocale function
removed unused privleges
added security checks to node controller
fixed rebasing conflicts
added entry to changelog
cleaned code