Abstraction: Render pass

[Nielsbishere]

A renderpass is defined as:
BeginRenderPass: Framebuffer & RenderPass
(N-1) x NextSubPass
... //Render calls for that subpass
EndRenderPass

The render pass has to define what layouts it comes from and goes towards. It also has to specify if it clears, doesn't care or keeps color/depth/stencil.
It has to define what outputs and inputs each subpass takes and how every subpass treats them.

It links to the frame buffer passed to BeginRenderPass by using the output parameters from the subpass.