Allow start/end year of date-picker to be set through w2ui.settings

Date-picker star and end years are hard-coded (1950 and 2020, respectively). This patch allows one to set those parameters as

  w2utils.settings['dateStartYear'] = 1800;
  w2utils.settings['dateEndYear'] = 2014;

thus, not limiting the possible range of date-picker's dates to 1950-2020