Update to potions WIP

Fixes #1796. I've gone through everything & renamed all the potions to something useful.

Still to go:
 
* Player flashes while potion is in use
* Some way of telling player of potions effects
* Clearer images for inventory so you can see which color you're picking

I've also noticed that if you use the dud potion (currently black potion) & get the no jump option sprite and try to jump, you can still get Abed's jumping sprite to flash up very briefly.