Extract replicator and utils to a separate project

This PR is motivated by #325. The replicator, the log, their utils and codecs, and their .proto specs have been moved to OhmData/c5-replicator (tentative name). This project now pulls them in as dependencies, referring to a maven repository hosted at https://github.com/OhmData/c5-replicator/tree/mvn-repo/ . Wherever I wasn't sure whether to keep a dependency (such as a utility class) here or move it there, I moved it. The README is updated to reflect the change.

NB: Issues are still open here related to the replicator and the log.