added ability to change blank history in a bulk manner
added ability to change blank history in a bulk manner

NMGRL/pychron,NMGRL/pychron,USGSDenverPychron/pychron,UManPychron/pychron,UManPychron/pychron,UManPychron/pychron,USGSDenverPychron/pychron,NMGRL/pychron,NMGRL/pychron,USGSDenverPychron/pychron,UManPychron/pychron,USGSDenverPychron/pychron