* First API design (many features missing, including input attachments)
* Metal implementation (no OpenGL yet)
* Render-to-texture demo (a little broken until we have depth buffers)
* Update examples to use render passes
This adds support for "natively defined" API types like callbacks that
will have to be implemented manually for each target language. Also this
splits the concept of "native method" into a set of native methods per
language.
Removes the "Synchronous error" concept that was used to make builders
work in the maybe Monad, this will have to be reinroduced with builder
callbacks.