Refactor POINT() to use on-the-fly arrays.

Add:
	src/graphics/matrix.(c, h)
		-Redefine `POINT()` to produce an on-the-fly array, instead of calling
		`createPoint()`. Now, the only function that calls `createPoint()` is
		`addPoint()`, which needs to add an allocated `Point_t` to a `Matrix_t`.
		-Does away with memory-management hell (ie, unnecessary calls to
		`COPY_POINT()`).
		-Redefine `addRectangularPrism()` to accept `Point_t` arguments.