mergecopies: add logic to process incomplete data We first combine incomplete copies on the two sides of the topological CA into complete copies. Any leftover incomplete copies are then combined with the incomplete divergences to reconstruct divergences spanning over the topological CA. Finally we promote any divergences falsely flagged as incomplete to full divergences. Right now, there is nothing generating incomplete copy/divergence data, so this code does nothing. Changes to _checkcopies to populate these dicts are coming later in this series.