Claim Gantt repo as currently for testing purposes

There is currently a bit of confusion around Gantt Git repository
where people think that Gantt is currently in use. We need to
explicity state that Gantt is solely for testing purpose and not
an active project.

Change-Id: Id50717c66ef65e69ae5ac8c134ee57e5e424d1e8
Merge "Claim Gantt repo as currently for testing purposes"