Merge / Split UI

Manual Merge/Split can be accomplished via direct editing of the Matchgrid, but it might be desirable (especially for ReconciliationManager and/or ReconciliationSupport level users) to have a "wizard-like" utility. eg:

1. Pick subject (probably via Matchgrid > display or search)
2. Select "Merge" or "Split"
3. Split only makes sense if the Reference ID is also associated with another row. If so, rematch (maybe that's really Merge?) or offer to create a new Reference ID.
4. Merge requires picking another subject, then deciding which Reference ID to keep.