More Basic Health Stuff

Filled out the increase/decrease health methods in Entity
Allowing a Damage Amount by Height

Modified Walking Enemy to take damage upon landing, and for this damage
to be directly related to the maximum height of their fall
Enemy Affected by Dropping

The enemy will be affected by dropping, and will no longer progress to
wall. Issues: Need to find actual max Flick Height, remove render upon
death/make splat.
Created Castle Class

Created a class for the castle with basic functions.
Final Health Touches

Enemies can now "die" (their shadow is left on the field). Castle also
affected by enemies at the wall.
Death Stage with Game Restart added

Now when you die, you are brought to a death screen with a message and a
main menu button.
Merge branch 'Health'