adds a time interval picker sourced from...
adds a time interval picker sourced from https://stackoverflow.com/questions/27229168/selecting-a-period-or-a-date-using-one-javafx-8-datepicker
adds a time interval picker sourced from https://stackoverflow.com/questions/27229168/selecting-a-period-or-a-date-using-one-javafx-8-datepicker