Health is now displayed in a heart meter in the HUD, plus a bar under
each damaged entity.
Implemented a knock-back component so that entities will be pushed back
when hit.
Each item use reduces the item's health by 1, eventually leading to it
breaking.  Wooden Sword's health was increased accordingly, allowing
enough uses to create slightly more than 1 new Wooden Sword.
Merge branch 'master' of https://github.com/treytomes/ASCIIWorld.git

Conflicts:
	ASCIIWorld/src/asciiWorld/chunks/Chunk.java