FEATURE - Moderators can create and manage groups (#10432)

Enabling the moderators_manage_categories_and_groups site setting will allow moderator users to create/manage groups.

* show New Group form to moderators

* Allow moderators to update groups and read logs, where appropriate

* Rename site setting from create -> manage

* improved tests

* Migration should rename old log entries

* Log group changes, even if those changes mean you can no longer see the group

* Slight reshuffle

* RouteTo /g if they no longer have permissions to view group

app/controllers/admin/groups_controller.rb

@@ -37,6 +37,8 @@ class Admin::GroupsController < Admin::AdminController
   end
 
   def create
+    guardian.ensure_can_create_group!
+
     attributes = group_params.to_h.except(:owner_usernames, :usernames)
     group = Group.new(attributes)