Shocking animations

![shocked](https://cloud.githubusercontent.com/assets/5659269/5426450/dfdb3f5e-831f-11e4-9fab-d5ad06aaad16.gif)
Adds animations for being shocked. Affected mobs will convulse for a moment before falling down. After collapsing, the stun will have its normal duration - shocked mobs will also shake around a bit after falling.