include/erltrek.hrl: make course and speed numbers()

* Allow both integer() and float() for
  #ship_data.course, #ship_data.number and
  #ship_state.speed
Update typespec in erltrek_galaxy.erl

* Fix typespec of
  update_sector/{3,4}, lookup_sector/{2,3}
  place_object/2, place_object_quad/2, update_ship_pos/1

* Fix result type inconsistency of
  place_object/2, place_object_quad/2