RON RDT: Version Vector

https://en.wikipedia.org/wiki/Version_vector

A version vector is a set of timestamps, one timestamp for each replica. In RON, this set is formed of UUIDs.

1. Type UUID

RON text:

vv

Hexadecimal:

0x 0eba 0000 0000 0000
   0000 0000 0000 0000

event encodes timestamp. ref is 0. payload is empty.

Replica alfa measures its local time as 23 and creates a version vector:
```
*vv #23+alfa @23+alfa :0 !
```
Replica bravo measures its local time as 27 and adds it to the object #23+alfa:
```
*vv #23+alfa @27+bravo :0 !
```

Reduced chunks ops use the same format as raw ops.
The order of fields doesn't matter. For reproducibility, ops should be sorted by event origin.

Version vector object is normally created with exactly one measurement:

*vv #42+charlie @42+charlie :0 !
*vv #42+charlie @42+charlie :0 ,

the same with compression:

*vv #42+charlie @42+charlie :0 !
                               ,

or with even more compression

*vv#42+charlie@`!,

The same as the value encoding.

For each replica in a value or patch there must be exactly one op with corresponding event origin if the replica has commited to the vector, and none otherwise.
The result op for each origin is selected by the LWW rule — which event value is greater.