Cosm with bodies only

TODO:

• Switch to using a reference to the geoid Make sure that the Geoids can be copied so we avoid the .clone everywhere
• Update documentation which is now totally broken
• Rename the Body trait to Frame because it's actually a frame not a body
• In cosm.rs check that the destination frame is identical to the storage frame, and if not, convert.
• Consider providing a with_units state clone which uses the uom package. Too annoying
• Add GMAT ICRF rotation (hint: check if they use their own MJD which is off by a few thousand days). Then reenable the ICRF rotation for the ground stations. Let's wait until Cosm supports AXBs. It will be a good test of AXBs anyway.