GC Optimizations / Reduction of Memory Footprint 

Included are a number of optimizations for the memory / gc profile of the Particle system.

I've also removed the "optimizations" that were in place for `cc.size` and `cc.p` which actually resulted in bad garbage collection behavior due to huge numbers of hash maps being created.

Creating the normal `cc.Point` and `cc.Size` instances will be a lot more efficient in modern Browsers due to "hidden-classes" anyways (See this Talk from Google IO 12 http://youtu.be/UJPdhx5zTaw?t=11m24s )