Feature/edit metadata authorization

I assume that pds_handle contain user group name(s) and thus we don't need to add roles. To reflect this I added customized method "groups" to user model. If the assumption is incorrect I will fix it and edit roles file.

@ekate When I run this line `Then the record should not have link "Edit"` it always fails for me. I believe that because even though you are logged in as an FDA cataloger you've set the permissions for the records `edit_groups` to public so everyone should see the edit link. 

Am I understanding this correctly? Or are you getting this test passing for you?