Replace interstellar-objects trajectory with hyperbolic orbit definition

[ajtribick]

Not sure what license the .ssc file is under, so not annotating it for now. @SevenSpheres if you have further information here, will add the SPDX-FileCopyrightText and SPDX-License-Identiifer tags.

In any case, removing the xyzv files means two fewer files to worry about tracking down license information.

Potentially could move this file to the data directory?

Breaks 1.6.x compatibility.

[pedro-fixingstuff]

Would using periods in years keep them compatible with 1.6.x?

I see you did round the parameter values from the sources, While I think storing all of them as we've been doing so far for other data files isn't ideal (especially due to Celestia's single-precision floating point arithmetic), I believe we should reach an agreement on this before other files are updated.

[ajtribick]

Potentially. The velocity calculations for hyperbolic orbits in 1.6.x were completely wrong, which could affect some of the orbit rendering code in unpredictable ways.

[SevenSpheres]

• Anyone contributing to this repository automatically releases their own contributions under the GPL.
• If that's not sufficient, I release all my contributions to CelestiaContent under CC-BY.
• As with many ssc files, some content is taken from Celestia Origin. You can discuss with them if they want to release it under a different license.

[mattiaverga]

• Anyone contributing to this repository automatically releases their own contributions under the GPL.

Well, not necessarily... AFAIK in order to be "legally conformant" a DCO signing requirement should be enforced.
https://opensource.com/article/18/3/cla-vs-dco-whats-difference