tests: Add internal test for the weston test screenshot capability

This also serves as a proof of concept of the screen capture
functionality and as a demo for snapshot-based rendering verification.
Implements screenshot saving clientside in the test itself.

This also demonstrates use of test-specific configuration files, in this
case to disable fadein animations and background images.

Signed-off-by: Bryce Harrington <bryce@osg.samsung.com>
Reviewed-By: Derek Foreman <derekf@osg.samsung.com>
4 files changed