CCSDS OEM Import is slow, export not yet available

[ChristopherRabotin]

High level description

Loading a large OEM is slow and clunky. And there is no way to export a trajectory into an OEM file. The latter is currently planned in ANISE, but eventually, the Traj<_> trait will work smoothly with ANISE.

Requirements

We need to export a CCSDS OEM file from a propagated trajectory. It may be worth considering an initial implementation of #87 as well.

Test plans

• Ensure that we can export a Traj to a CCSDS file
• Add a benchmark to show how speedy or slow reading a CCSDS OEM file is.

Design

General ideas:

1. Using a bufreader instead of reading the whole file at once (this was obviously a hacky implementation)
2. Token checking should be done against a HashSet to get O(1) performance on checking instead of current O(n)

Breaking changes:

• It may be worth considering dropping the TrajectoryLoader class in Python entirely and only use the OrbitTraj to load a CCSDS trajectory. Keep in mind that the ability to pickle classes in Python is vital to workflow development.