Add screen viewer state update feature

Add screen viewer state update feature

In screen-connector multi viewer senario, provider should decide it's
resume/pause state using every viewer's visibility. So, every viewer should
share their visibility to AMD.

Requires:
 - https://review.tizen.org/gerrit/#/c/137133/ (aul-1)
 - https://review.tizen.org/gerrit/#/c/137134/ (amd)
 - https://review.tizen.org/gerrit/#/c/137136/ (widget-viewer)
 - https://review.tizen.org/gerrit/#/c/137437/ (appcore-watch)

Change-Id: I6437586abe67f732aa302ebca0d4c06613405d07
Signed-off-by: Hyunho Kang <hhstark.kang@samsung.com>