Helper tool to expand hitboxes

* Moved all icons from icons/ to icons_raw/

* Added a script that generates icons/ from icons_raw/ by expanding the hitboxes on each icon.

This script resides at tools/HitboxExpander/hitbox_expander.py. Hitboxes are frustrating, no one wants to spill his virus culture bottle by accidentally clicking a 1-pixel hole inside the Pandemic. We should give this script a shot and modify/revert if issues arise.