Implement cloning and serialization of P3 correctly

[mkommend]

Currently, the internal state of the P3 algorithm during execution is neither cloned nor serialized that in turn hampers the usability of P3 and is an unusual behavior in HL.

[mkommend]

r15301: Corrected cloning and serializing of P3 and associated classes.

[abeham]

Reviewed the changes in r15301. I have one comment (that I don't think is necessary to consider here, but for future): The multi-dimensional jagged array occurrances could be cloned in a single line, similar to how you clone clusters, e.g.

occurances = original.occurances.Select(x => x == null ? null : x.Select(y => y.ToArray()).ToArray()).ToArray();

[mkommend]

r15324: Merged r15301 into stable.