Allow bitly_retrieve_groups to retrieve the "general" group list
Allow bitly_retrieve_groups to retrieve the "general" group list

`bitly_retrieve_groups` had a `stop` check on `organization_id` that prevented the function from being able to pull the "general" list of groups (not by organization)
 - Make default for `organization_id` = NULL which is ignored in request and pulls general group list
 - If `organization_id` is present it will pull the groups within the organization as expected
dmpe/rbitly,dmpe/urlshorteneR