Shield/sword enemy

[molyholy]

The shield/sword enemy should:
-be idle normally, then head towards the player when she gets close enough
-have a "raise shield" state and is essentially invincible
-during the raise shield state, should turn and face the player wherever she goes so she can't circle around and attack from the back
-have an attack state where he raises his sword to attack. This should be slow-ish, to give the player an opportunity to attack. This should be the only opportunity when the player can attack.