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 I think you're correct that Esha's custom permissions are probably redundant but it didn't occur to me since these stories were being done in parallel.

Even though we don't know what the desired behavior is, I don't think it would ever be that all users regardless of being authenticated or authorized can edit all the GIS records. I would default that to `read_groups` to include public and not specifying an `edit_group` for now would default to no access. We probably want to err on the side of less access as opposed to more.