Refactor PLYProperty to encapsulate data and methods for property header, parsing, data management.
Refactor PLYElement to encapsulate data and methods for property header, parsing, data management.
Refactor PLYObject to use new implementations of PLYElement and PLYProperty
Add data type & size getters to PLYElement
Update unit tests
Merge branch 'exp'

Conflicts:
	PLYObject/PLYObject/PLYElement.h
	PLYObject/PLYObject/PLYObject.h
	PLYObject/PLYObject/PLYObject.m
	PLYObject/PLYObject/PLYProperty.h
	PLYObject/PLYObject/PLYProperty.m
	PLYObject/PLYObjectTests/PLYObjectTests.m