Brain background & animations

Sprites are again iffy -- discoloration and text comes from the fact I'm
using the free version of TexturePacker.

(To see lungs, change "stage.setBrain()" to "stage.setLungs()" in
CombatPage).
Brain sprites scaled

Animation issues may come from the fact I loaded all 3 kinds of neurons
-- 60, 40, and 80.