Simplification and display tweaks

 * simplify (a lot) using update_and_get_changes()
 * cleanup some old comments & such
 * csbt_save::_get_record_extras() adds 'display_name'
 * minor tests to avoid PHP warnings/errors
 * partially fixes issue with updates resetting changes in progress (#42): only changed values get updated now (if those are being changed, the bug will still occur)