Cleaned up Sprites for reduced drawcalls.

Enemy fish no longer have 4 game objects for their eyes.
Enemy fish are no longer grayscale, and all fish sprites are
packed into one sheet.
Main fish now uses same texture as other fish for reduced drawcalls.
Fixed added shader to seaweed that bloated its drawcalls.
Reduced drawcalls on whale by packing his sprites.
Condensed my sprite sheet to not be a power of 2 but use less space.

I'm not sure whether this actually saves me anything, as Unity
may scale up the file internally.
Removed extra unused sprites.
Removed unused materials.
Merge branch 'reduce_drawcalls'

Conflicts:
	Assets/_Scenes/Game.unity