webos-image: Inherit core-image and remove duplicated stuff

Open-webOS-DCO-1.0-Signed-off-by: Martin Jansa <Martin.Jansa@lge.com>
Open-webOS-DCO-1.0-Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Change-Id: I695344f4030ee8a7b58aa3bf1632c2bc03e54885
Reviewed-on: https://g2g.palm.com/1892
Reviewed-by: Martin Jansa <Martin.Jansa@lge.com>
Tested-by: Martin Jansa <Martin.Jansa@lge.com>
Reviewed-by: Herb Kuta <herb.kuta@lge.com>
Reviewed-by: Iyad Qumei <iyad.qumei@palm.com>
Reviewed-by: Susan Montooth <susan.montooth@lge.com>