Add 'gdash' to git-deploy

gdash is currently deployed from files/graphite/gdash-app/ in the Puppet
repository. Deploying it in a sensible way has been a TODO for a while.
The repository itself is operations/software/gdash, but I didn't see where
to specify that.

Bug: 53377
Change-Id: I4c088cf5e7faa8648133ea1fa3416b978fb835ed