Add MD-SAL artifacts

This migrates the version declarations into mdsal-artifacts artifact,
such that they can be imported by downstream projects. This will be
shuffled again as we define the scope more.

Change-Id: Ie97584dd477b786e3fc4f6d79a174425c020fa0c
Signed-off-by: Robert Varga <rovarga@cisco.com>
Merge "Add MD-SAL artifacts"