SaVi satellite constellation visualizer savi-dev

Adding in menu option for tropics flag.

fixed drawing of tropics for spherical/cylindrical projections,
which need -all-maps flag to even see.

Adding sanity-checking to parameters, and forcing to floating point
so problems don't crop up unexpectedly wth later calculations.

Adding in a 'tropics' flag and checkbox in coverage, to show the Tropics of Cancer and Capricorn.
This can be altered in the Simulation Constants dialog.

Not supporting cylindrical/spherical projections yet, because the trig manipulation escapes me.
So it's unprojected only for now.

Noting unicode support prototype.
Likely a dead end.

Forcing equatorial plane on for equatorial systems.

Minor demonstration of how Unicode support might be done.
Looks painful, but is backwards compatible, easy to override.

lower-case minor text fix.

Adding in option to show equator in coverage view,
with new checkbox/menu option.

This is synced to the equatorial plane view in Geomview.

(Should have gotten this working loooong ago - turned
out to be much easier than I had thought.)

Noting unsuccessful unicode experiments.