Created RevisionResolver implementation that uses maven version

Configured with a groupId and artifactId, it uses the maven version of that
artifact as the revision number

Issue #AXON-171 Fixed
CommandGateway should use callback when a RetryScheduler is configured

Using a callback will trigger a retry when an error occurs. Fire-and-forget
methods will use a LoggingCallback in the background.

Issue #AXON-170 Comment