- Consumer: better logging of offsets retrieved

- Serializer: fix bug de-serializing null string
- Router: make NewBrokers a replay subject replaying all broker instances
- Router: retry fetching of partition offsets up to 4 times
- Router: don't let absence of OnPermError cause null reference exception
- Tests: create test for consuming on non-existent topic
- Tests: fix read offsets test
- Tests: fix ListenerRecovery test
- Tests: fix IsBrokerResponding test to catch socket exception