Rename `neglect_tps` to `orbit_dataset`

Closes #63 (closed)

• Rename parameter neglect_tps to orbit_dataset, with accepted values tps/ppr and tcb/ltt
• When using an orbit file, save the value on self and conditionally select the datasets that we use
• When using static or custom PPRs, ignore the parameter and save it as None on self, and do not issue any warning