Make the renderer and IPC aware of multiple projection and quad layers
using the layer renderer.
Remove redundant code related to idle images and imported buffers and
command buffer rebuild, since we now always just display the layer
renderer's frame buffer.
Get view and projection properties from xrt_device.
Version 2 additions by Jakob, still use a semaphore to wake up the client.
But now instead call the compositor wait frame and have that thread wake up
the client, and return immediatly on the IPC channel.
