Add ability to add a resource to the group at the specific position

* Add ability to add a resource to the group at the specific position.
* Add ability to move the resource within the group to the specific
  position.
Fix adding resource to a group

* Verify there is no resource/clone/master with id group_name when
  creating a new group.
* resource_group_add function does not push the cib to the cluster
  any more.
* Unnecessary variables have been removed from resource_group_add
  function