Increase range of GLwindowSolarMap's orthogonal projection depth

The solar map window assumes the solar system's csrad parameter is
properly set to contain all celestial objects in that system.
There are no practical need to limit depth of the projection since
the window does not use depth buffer.

Alpha Centauri solar system in space_debug.ssd was revived and
adjusted to have proper coordsys radius for demonstration.

We also add a test mission script which starts from Alpha Centauri
system.
refactor: Encourage RAII in GLwindowSolarMap::drawMapCSOrbit()

The source is fairly old and not cleanly converted from C to C++.
There are many things we could improve about the source.
Tweak orbit line segment count in solarmap using scale-based LOD

Also deleted duplicate codes that tried to render the orbit since
we have already drawn the orbits in drawMapCSOrbit.