Added CommandManager.make_group_query_tree_message() method.
Added CommandManager.make_group_query_tree_message() method.

Pulgama/supriya,andrewyoung1991/supriya,Pulgama/supriya,josiah-wolf-oberholtzer/supriya,Pulgama/supriya,Pulgama/supriya,andrewyoung1991/supriya,andrewyoung1991/supriya