Minor improvements to orbit determination types

[moeyensj]

• Uses adam_core's OrbitDeterminationObservations class as inputs to the low level IOD and OD functions
• Modifies the FittedOrbits and FittedOrbitMembers classes to match those used by adam_core (we can full replace them at a later date)
• Adds calculate_max_outliers
• Fixes how the propagator is passed to differential correction and the orbit merging functions