Use less confusing vocabular

[ewoutp]

Use log messages like:

"Serving as a Starter master"
"Serving as a Starter slave"
"Just became master of the Starter Cluster"
"Tried to become master of the Starter Cluster but failed: Status 412"

To make the distinction between ArangoDB & ArangoStarter as clear as possible

[Simran-B]

Would be beneficial if there was a synonym for cluster to make the distinction between starter cluster and arango cluster even clearer, but all I can think of are grid and group - and neither is really fitting. Perhaps something more abstract would work, like Starter net? It kind of implies a network of peers though, and not a master/slave architecture.