Conversion to using agl-compositor

Conversion to using agl-compositor

- Use Qt/QtWayland to set-up an app_id for the main surface. We use that
  surface and pass it to waylandsink. Waylandsink create a sub-surface
  with the parent the Qt/QtWayland one.

- Install a handler for handling bus messages With it, it allows to pass
  the wl_display with the help of a context and the surface backing up
  the Widget.

- Installs a timer to wait for Qt to create/get the xdg_surface and
  attach a buffer to it.  Without we won't be able receive the commit
  for the parent event in order to handle it.

Bug-AGL: SPEC-3382

Signed-off-by: Marius Vlad <marius.vlad@collabora.com>
Change-Id: I1574a1d21b8d12649b77cfe098f8141d09de9ee9