ivi-shell: introduce ivi_layout_view

ivi-shell: introduce ivi_layout_view

This patch introduces ivi_layout_view data struct,
which is a wrapper of weston_view.

There is always only one ivi_layout_view for an
ivi_layout_surface and ivi_layout_layer pair.
A surface could have many views with different
geometry and transformations, so that a surface
can be shown on:
	1. On many screens
	2. On the same screen with different positions

The geometry of a view is modified, when properties of
its layer are changed through ivi_layout_interface.
Users of ivi_layout_interface does not have direct access
to ivi_layout_view structure.

v2 changes:
	1. Use ivi_view_is_rendered function instead of
	   active member
	2. Add descriptions to introduced members of
	   structs

Signed-off-by: Emre Ucan <eucan@de.adit-jv.com>
[Natsume: add empty line]
Reviewed-by: Wataru Natsume <wnatsume@jp.adit-jv.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>