Kludge for ensuring INNER JOIN field/col from "primary" table exists.

See `qColsToSelectInNewTable.EnqueueIfNotContains(strNewField);` from _processInnerJoin in SelectCommand to see how the "primary" table is treated differently.  Just need to do the same thing for the initial DataTable to remove this kludge.

That said, this just again goes to show that the way I'm parsing SQL is inane. As I've mentioned earlier, borrowing Irony (https://irony.codeplex.com/) would be smart, I think.