Got rid of keyColumn
Now key is directly the keyColumn name, e.g. key is asu_id not asu
This makes things less confusing and simpler.
We've done this following last commit of DataDistribution to also change the ways we deal with key/keyColumn.
Note that now the checkKeyCounts and checkDifferingKeys are using to get the keyTable name a ClusterConnection object and the new ClusterConnection method getTableOnNode