Standalone compositor based on Green Island

It is much easier to develop the QML compositor as a standalone
executable rather than a plugin.

Green Island will be used as a library and QtQuick plugin to extend
the QtCompositor API.

Issue: #82
Run starthawaii from compositor

Update compositor to recent changes, we now launch a startup script.

Issue: #82
Remove FluidCore import from compositor

Issue: #82
Rename DesktopCompositor to Compositor

Issue: #82
Pass wl_display to Shell and Notifications constructors

Issue: #82
Set compositor window geometry at startup

We are using the compositor in windowed mode in this phase, set
a sane geometry at startup.

Issue: #82
Send loaded event when interface is bound

This will make the shell load the user interface.

Issue: #82