Rename desktop protocol to avoid conflicts when using qtwaylandscanner

qtwaylandscanner recognize the qt_ and wl_ prefix for interface names
and strip them away when generating server-side code.

The hawaii_desktop_shell interface becomes wl_hawaii_shell since it will
be reused for all kind of shells and the desktop protocol becomes hawaii.

Every interface starting with hawaii now starts with wl_hawaii.
Rename desktop-shell.xml to hawaii.xml

Follow protocol and interfaces renames.
Rename interfaces for Weston plugin

Follow recent renames.
Rename interfaces for shell

Follow recent renames.
Use qtwaylandscanner for Green Island plugin

Issue: #82