editor_services was growing into one interface every tool depended on
whole. It splits into the roles the editor plays for its tools: the
selection, the view, the undo history, the templates by the track, the
ground with the terrain model, the track design and the guide of the
first steps. Each tool is handed only the roles it uses, so what it
depends on can be read from its constructor; editor_services stays as
the sum of the roles the editor implements.
The third tool out of editor_mode. It reaches the terrain model and the
places of the tracks on it through the services, the place of a track
for the terrain model is a type of its own now, and the laying and the
switches ask the tool for the kink it allows. A self-test command can
ask to be run again in the next frame, as the check against the terrain
model does while the model comes in.
