Add GetProperty and SetProperty stages

• support setting

  • static float,
  • static integer,
  • time_stamp (current time),
  • text,
  • increment a (previously added integer) counter

• supports getting

  • float, integer, time_stamp and text
  • duration between a previously set time_stamp
  • all properties

• props can then be

  • printed
  • written to file (either all or only latest)