Datatable

Added row selection to the datatable.  

Not totally happy about it.  I wonder if I should ask the records in the data to have unique ids to make it easy to identify the selected records.  Right now, I add unique identifiers if none are available.  Perhaps I should hide those.   

I have not yet fully though about paging or infinite scrolling which might continuously add records to the table, or might hide selected records from view.  That is partly the reason for requiring unique ids, so that the selection can be persisted even when the record is not visible (paged out or occluded)