Approach to message size is not consistent in clone protocol

[gsvarovsky]

In the transport-independent clone-clone interface (see TS interface in JS engine)

• Individual published operations are of (potentially) restricted size and are modelled as one "message"
• Recovery operations are of arbitrary size (may be fused) and are modelled as one message
• Snapshots are also of arbitrary size (usually, but not necessarily, bigger), but are modelled as a stream

The protocol could be more abstract and treat a snapshot as one coherent message, or all messages as streams.

(Arose in consideration of proximate causes to an agreement, see security project design)