Inventory + stuff

Added;
- Highlight for selected slot
- Delete button in inventory
- Started: Derpy sprite change depending on movement

Bugs:
- Derpy's sprites do not change correctly
Merge remote-tracking branch 'origin/Branch_0.04' into Branch_0.04

Conflicts:

Equestrian_Eclipse_Fall_Of_An_Empire.gmx/Equestrian_Eclipse_Fall_Of_An_Empire.project.gmx