Clean up addPolygon() methods, add documentation.

Add:
	src/matrix.(c, h)
		-add addHalfPolygon() macro to complement addPolygonFull().

Rem:
	src/matrix.c
		-remove individual addPolygon() and addHalfPolygon() functions, in favor
		of an addPolygonFull(), which intakes an angle argument that can be
		tailored to create either half or full polygons as necessary.