D translation of the libnova celestial mechanics engine.

The code is basically just a translation of the libnova sources into D modules. Original examples have also been translated to D, see the examples directory.

The original libnova code was forked from https://github.com/efalk/libnova @ 85f8817 (r0.16.0)

Copyright for the original libnova code is Liam Girdwood et al, please see authors.

I originally wanted to just create D wrappers around the original libnova code, but building libnova on Windows proved to be more challenging than anticipated, so I just went full D :)

• add unit tests from here
• add coverage

• v0.16.0 Initial translation from original C code to D.