This reconciles lp:~kdub/mir/android-client-buffer/ with the changes that have happened on trunk today.
a few points moved PixelFormat into geometry from compositor, and use mir/geometry on the client side as well. The concepts of dimensions and pixelformats are useful on the client and server side. (caused a bit of code churn)
this mp does not connect MirMemoryRegion into mir::client::MemoryRegion. (future mp)