Add SITE data type in Almanac

[ChristopherRabotin]

High level description

Almanac currently includes Planetary, Spacecraft, and Euler Parameter datasets. This task aims to add a new type called SiteDataset which defines locations akin to SPICE's SITE kernels.

These must include a name and an ID (or either, using the lookup table structure), and either latitude, longitude, altitude coordinates, or a position. Eventually this should support velocities to model tectonic plate movements like in SPICE's definition of the DSS antennas.

Requirements

• Add a Site dataset type
• Compute line of sight occultation from these dataset types

Test plans

• Normal serde tests as done in all other datasets
• Test with SPICE's occult if I can figure out how to call the point approach, cf. Help needed for gfoclt_c call GregoireHENRY/rust-spice#18 (comment) .

Design

TDB