Add ArcherTower defense
Modify Structure and Defense framework to accomodate Enemies
Modify to identify shooting Entity
Merge branch 'structures'

Conflicts:
	src/Fireblast.java
	src/Structure.java
Fix mouse listener for projectile shooting
Lower speed of player and projectiles.
Increase window size
Clarify x vs gridX
Add Grid and allow Entities to be added to GamePanel
Update Defense and Enemy. Add QuakeTower defense.
Merge branch 'grid'

Conflicts:
	src/Barrage.java
	src/Defense.java
	src/Structure.java
Merge branch 'spells'

Conflicts:
	src/GamePanel.java
Merge branch 'structures'

Conflicts:
	src/Defense.java
Make all Entities accessible through Grid
Merge branch 'spells'

Conflicts:
	src/Fireblast.java
	src/GamePanel.java
	src/Spell.java
Add images for QuakeTower and ArcherTower
Change all int coordinates to doubles. Fix exception with no enemies in
proximity.
Cast position to int
Fix dx rounding problem
Basic collision detection for projectile