Change the way getAGBarcodeDetails returns data

Now returns a dict keyed by column header rather than an ordered tuple
Modify how ag_edit_barcode gets barcode details

Expects dict keyed by column header rather than ordered tuple.
Also, add warning about changing participant name.
Updating a participant's name now updates samples

If the participant's name changes, then the samples associated with the old
name are now re-associated with the new name.