Fixed GetWorldPos and GetLayerPos

They previously returned the world position under the assumption that
none of the nodes in the hierarchy were rotated.
Included PimParticleSystem in Pim.h
Changed Vec2 and Color interpolation

They may (or may not) have worked before, but now they most certainly
work.
Mulitiple bug fixed and improvments to the particle system

Position types have been added. Lifetime is now customizable. Added
more clarifying comments.
OSX project files update

Bladi bladi bla.