this widget tries to replace efl.ui.stack efl.ui.flip & efl.ui.pager
In general those widgets do the same thing, they get content. And
display them with some sort of animations. The new idea here is, that
the basic widget active_view only handles the ownership etc. of the
content that gets added to this. Then there is a view_manager object. The
view_manager object gets notified over the new contents, and requests for
displaying particular contents. The transition then handles those
things.
The version here is feature complete with Efl.Ui.Stack and Efl.Ui.Pager.
Additional features can be implemented in the corresponsing transition
classes. Examples and tests will follow
Reviewed-by: Jaehyun Cho <jae_hyun.cho@samsung.com>
Reviewed-by: Cedric BAIL <cedric.bail@free.fr>
Differential Revision: https://phab.enlightenment.org/D8784
