Source specific updater for Betty
autoformatting
Remove channels from removed channel groups
Merge pull request #567 from atlasapi/bt-channels-remove-old-channel-group-channels

Remove channels from removed channel groups
Must remove channel groups from channels

Removing channels from channel groups does not remove from the
channel, so we must remove the channel group from the channel
Merge pull request #568 from atlasapi/bt-channel-group-remove-group

Must remove channel groups from channels
Merge pull request #562 from atlasapi/betty-equivalence

Betty equivalence
ContentMerger now has to have a topicsMergeStrategy!
ContentMerger now merges topics!
versionMergeStrategy could equally reasonably be KEEP
Merge topics based on offsets as well
KM data handler can just replace all topic refs
Row handler no longer needs to resolve topics

This was needed for a check I added to fix an earlier data mistake