Prepare Splout for allowing rolling upgrades

[ivanprado]

Currently Splout doesn't support rolling upgrades when beans related with API or with Hazelcast changes. This is mainly due to two limitations:

1. JSON serialization/deserializacion failing when not matching properties.
2. Hazelcast using Java Serialization

The first problem can be solved by tagging API beans with @JsonIgnoreProperties(ignoreUnknown = true) and develop upgrades carefully so that old systems keep working with new ones.

The second problem can be solved by using Hazelcast Portable for Hazelcast beans: http://docs.hazelcast.org/docs/latest/manual/html/portableserialization.html

Implementing that will allow to change slightly the API or some Hazelcast beans without needing to stop the whole cluster. Anyway, mayor changes still will need complete restarts.