Draw aids to navigation as buoys

A buoy, beacon, RACON, light or IALA mark in the vessel feed was drawn
as a ship. A vessel record whose type names one, or whose MMSI is an
aid-to-navigation station's (99MIDxxxx), is now isAidToNavigation and
vesselModelSpec draws it as the fleet set's buoy of its mark (cardinal
N/E/S/W, port or starboard hand, safe water, isolated danger, special
mark; a red can when the type names no mark), at its built size and
flagged fixed so its model does not turn to a heading. Its icon is a
disc instead of a chevron.

AISStream now subscribes to AidsToNavigationReport by default, and the
server names each report's aid type code (0 to 31) as its kind instead
of reading it as a ship type.

changelog.d/0000-buoy-models.md

@@ -0,0 +1,7 @@
+- Draw aids to navigation as buoys instead of ships: a buoy, beacon, RACON,
+  light or mark from the vessel feed (or any AIS station numbered 99MIDxxxx)
+  is now the fleet set's buoy of its IALA mark (cardinal, port or starboard
+  hand, safe water, isolated danger or special mark), standing still with no
+  heading, and its icon is a disc rather than a chevron. AISStream now
+  subscribes to aid-to-navigation reports and names each by its kind of mark
+  (samehkhamis, #0000).