Make the privilege control to work as expected. Using the

NodeListByNameCell for selecting the grantee.

This patch includes:
- Change the RolePrivilegesModel schema to allow to use the
  NodeListByNameCell for showing grantee, and granter information.
- When setting some value - do not use the silent flag in Select2Cell, which
  will allow the session manager to take the value in account, which is
  used by the NodeListByNameCell.
- Set the top object in the children of the UniqueControl collections.
  [Ashesh Vashi]
- Pass on the node information to the actual data model, so that - we can use
  node information by the control itself. [Ashesh Vashi]
- While adding the new privilege, set the granter to the current user.
  [Ashesh Vashi]

web/pgadmin/browser/server_groups/servers/__init__.py

@@ -115,7 +115,8 @@ class ServerModule(sg.ServerGroupPluginModule):
             {
             'name': 'pgadmin.browser.server.privilege',
             'path': url_for('browser.index') + 'server/static/js/privilege',
-            'when': self.node_type
+            'when': self.node_type,
+            'deps': ['pgadmin.browser.node.ui']
             },
             {
             'name': 'pgadmin.browser.server.variable',