Logical addresses: canonicalize UUIDs with IDs (shorts)

Instead of using UUIDs as addresses, the cluster members should agree on shorts, e.g. 1 for A, 2 for B and so on, and use these instead of UUIDs.

This happens after a certain warmup time. E.g. the coord could assign these IDs, so they're unique.

IdAddress and UUID have to be able to do equals() or compareTo() with each other !

Advantage:

• we send a short (2 bytes) instead of a UUID (16 bytes)
• we use an IdAddress (class with a short) instead of a UUID. This is 6 bytes less per instance
• IdAddress might be faster with equals() and hashCode() than UUID