Implement `setRole` API to Window Manager.

Currenly, `requestSurface` with argument `role` is implemented to get surface ID from Window Manager.

But surface should not be visible to application because it is low level concept of wayland and weston. It should be abstracted to more high level concept.

Window Manager controls window state change according to role policy.

So setRole is better for application.

Application can do tha same as requestSurface by putting some parameter in the argument of json attached to setRole (current idea)