Placeholder Graphics, Spinning Cannon, etc

Added some placeholder graphics.
Also includes unfinished Weapon/Projectile system and AnimatedSprites
(was adding support for them for the Row Boats and maybe explosions).
Anti-Aliasing and Higher Res Placeholder Graphics
Cannon Continued, DisplayObject/Entity fixes, ...

Cannon now shoots out cannon balls. Started setting up the Aim
Assistance (the lines).
Fixed problems with how the Update List and DisplayObject children were
set up.
Moved FPS tracker to HeadsUpDisplay class.
Added two new Util functions (GetPointInDirection and Distance).