Add ConsensusRSMPolicy to minnietwitter example

[quinton-hoole]

1. Add AtLeastOnceRPCPolicy
2. Prevent main() from swallowing exceptions, so that gradle can actually report errors.
3. Adjust AtLeastOnceRPCPolicy default retry timeout from 5s to 10s

[quinton-hoole]

Addressed comments. Squashing and merging.