Rework key assignment for client windows

prepareAddWindow now returns the window ID to the client instead of
the client providing an id to sysmgr. Reason being a window now has
several buffers with different keys. Subject to change if we need an
additional buffer for the semaphore

Open-webOS-DCO-1.0-Signed-off-by: Florian Haenel <florian.hanel@palm.com>
Open-WebOS-DCO-1.0-Signed-Off-By: Simon Busch <morphis@gravedo.de>
Enable hybris support for tuna/grouper machine

Open-WebOS-DCO-1.0-Signed-Off-By: Simon Busch <morphis@gravedo.de>
Implement host window rendering through libhybris

This introduces a new server instance inside LunaSysMgr to accept shared rendering buffers
from remote clients like WebAppMgr. The central compositor instance accepts the buffers
and forwards them to the corresponding host window which wraps them into the right
rendering object of the UI.

Open-WebOS-DCO-1.0-Signed-Off-By: Simon Busch <morphis@gravedo.de>