- add put_model() function to place models at given lon/lat. If
elevation is nil, then it will be put on the surface. The path is
relative to $FG_ROOT.
- let geo.click_position() and geo.aircraft_position() return copies
of the Coord class, not just a reference
view.nas: adaptation for geo.nas change; minor changes
- simple geo coordinates class: geo.Coord with methods to set/get single
components, to apply distance/course and the get distance/course to other
coords
- functions that return click and aircraft position as geo.Coord
- function that returns tile_path for given lon/lat
- function that returns normalized angle (0 <= angle < 360)
