WebGL and TypedArrays support

As a follow up to #12, here is a first stab at implementing the WebGL specification.  It should be complete, but I've not exercised it much yet, so it may contain bugs and typos.

trait TypedArrayCommon[T] is used to prevent (even more) code duplication, but perhaps it should be somehow tucked away out of sight since it's not defined anywhere in the spec.

I would add documentation but I don't have anything to scrape MDN and pop it into the code, does anyone have something that does this, or at least reduces some of the work?

Comments/suggestions/style warnings all gratefully received.