[master] Support for rolling logs

This replaces #3009 that was messed up. 

Adds support for rolling logs. When the log is rolled over diagnostics information is added to the top of the new log.

Even if there's no use for the `shutdown` method a.t.m. I think we still want users to have that interaction point with the `BatchImporter` such that when we need something to be shut down the user code is already correct. Or you could change the BatchImporter to `extend org.neo4j.graphdb.Resource` (which is an `AutoCloseable` that throws no declared exception.