v2: add graphics examples

Closes #44 (meant to merge into `v2-dev` not `master`).

This PR moves the graphics examples from the [azul3d/examples](http://github.com/azul3d/examples) repository to a sub-directory `example`.

I think this works better: we can have `gfx` examples, `audio` examples, etc. We don't have to have a single repository with examples for everything inside it.