Cleanup Requirements code

[dj2]

The current code which passes the [require] information into the engines is ... not good. Need to refactor the code to make it easier to extend.

[dj2]

This is mostly done. The features and extensions are extracted and passed to the initializer. The fence_timeout is passed through an engine structure. The remaining two are the framebuffer and the depth/stencil buffer which should be extracted and added to a pipeline.

[dj2]

This is done with: #168