Moved authentication from Apache config (not visible) to PHP
* Authentication is only required/possible of you perform anything but an OPTIONS request over HTTPS (or over HTTP if running in a development environment)
* Authentication is not required if performing a GET, HEAD or POST on the users collection (but it is possible when using HTTPS)
* Authentication is not required if performing a GET or HEAD on the homepage url (but it is possible when using HTTPS)

This makes it possible to integrate SimpleSamlPHP (though this is not yet implemented)

Furthermore I fixed a bug in the beehub_directory view which still pointed to $directory (is now $this)
Homepage and 'sign up' page are now accessible for unauthenticated users
Fixed several bugs with 'virtual' resources which made them need a real file as if they were XFSResources