"Move under..." menu item for top-level groups (to make "Convert to Child" + "Move" a single operation)

[josh-berry]

Top-level groups should have a "Move under..." sub-menu, which moves the top-level group directly underneath the chosen group.

Today, this can only be accomplished in two steps: (1) Convert to Child Group, (2) Move the child group to its destination parent group.

This is annoying for those of us that maintain an "Archive" group or similar (or for anything that should remain in the stash but no longer be a top-level group).