Trebuchet : Add folder on folder checks

- Check if the new folder can accomodate all items
- Don't expand folder if trying to drop folder on folder

Change-Id: I208e3afd4ee6aeeea01928fc77e136d6085c4fdc
(cherry picked from commit 6903b919c835e9e6c9d3a0b6b7e61c31cd12e0ac)