hawaii.xml: Overlays are not shell surfaces anymore

Move it from wl_hawaii_shell_surface to wl_hawaii_shell because
overlays are going to be part of the design language of the shell
as we'll only have one thus it will be part of the main UI not
something that other applications will create.

The output argument is removed because the overlay is going to be
shown in the current active screen.

Issue: #148
server: Overlays

Treat overlays as other shell parts.
Also center them on the screen where the pointer currently is.

Issue: #148
compositor: Overlays

Treat overlays as other shell components.

Issue: #148
Move overlay to look and feel

Issue: #148
Merge look and feel with shell

We want shells and their components to be tightly integrated thus are
merge together.
Rename view QML files

View is redundant here.

Issue: #148
hawaii.xml: Update copyright
Remove wl_ prefix from Hawaii custom protocols

Issue: #148
containments-panel: Check whether the configuration button exists

Avoid errors when setting visibility and the button is not yet
available.
launcher: Temporary fix for missing panel context property

The panel context property was removed, this is a quick and dirty
fix something that will need to be fixed better later.