Remote-display windows for CES IC demo

Close for JJ RC1

Series has now landed. 

I've been modifying tbtnavi to rely QScreen and implicitly on xdg_output extension to retrieve the screen names and use it to move/migrate the surface to that output. The changes are currently in my sandbox branch.

The current WIP branch for this series contains the ability to specify it directly in the configuration file, without the need to modify the application (both the output and remote-output section will be aware of it), but I guess an example would be nice to have as an example – and tbtnavi contains that. Homescreen also contains code that which can help move/migrate to other outputs by using a environment variable. 

Lastly I've kept the same bit from weston patch, where the remote output is enabled after the DRM ones. This makes it such that client shell is always started on the primary output without any hassle to configure it. Later enabling the (remote) output will make the client shell always use the DRM ones before the 'remoting' one. 

Amended a few bits and piece that I found useful, mostly in terms of sanity and checks. 

Pushed changes for this at https://gerrit.automotivelinux.org/gerrit/gitweb?p=src%2Fagl-compositor.git;a=shortlog;h=refs%2Fheads%2Fsandbox%2Fmvlad%2Fremote-surfaces. Waiting now for https://lf-automotivelinux.atlassian.net/browse/SPEC-3334#icft=SPEC-3334 to go in as it builds/works on top of that as both of the touch same parts, including protocol. 

Ping? Any further comments? I'm pretty ready much to submit a version of this. @knimitz, @Tadao Tanikawa have you any managed to go over the code and docs?