Groundskeeper 0.19.1

Added

• An Unraid Docker template (deploy/unraid/groundskeeper.xml): a container made from it shows in Unraid's
  Docker tab like any other app, with the update check, autostart and Edit, instead of "3rd Party".
• A heading arrow on the robot dot (Live map): an arrowhead inside the dot points where the robot is heading,
  and stays true when the map is rotated.

Changed

• The 3D robot and Follow use every position the robot sends (about one a second while the phone app is open)
  instead of only the status every 1.5 s, and take them in the robot's own time order: after a network dropout,
  the late positions in the robot's backlog are skipped instead of sending the 3D robot back on a detour. The 2D
  robot dot still moves with the status.