bundle: deconflate stage_row_added from tracked_row

[erichanson]

Make it so stage_row_add pulls from tracked_row, not just some random row in the db. First you track, then you stage. A tracked row is a row who is within a bundle's scope of concern.

• bundle.tracked_row_add(bundle_name, schema_name, relation_name, pk_name, pk_value) adds a row to bundle.tracked_row_added table.
• bundle.tracked_row_added is a table that contains newly tracked rows, which are put there by bundle.tracked_row_add()
• bundle.tracked_row is a view that unions rows from bundle.head_commit_row, stage_row_added and tracked_row_added.

Now, stage_row_add() should check that the row exists in tracked_row_added.