Move ingest_parallax function here from SIMPLE

[kelle]

@Exu-112 has written an excellent ingest_parallax function and tests. The function has good error handling and deals with the adopted column. Parallax table already exists in the template so makes sense to move this function over. Probably best to go ahead and start an astrometry.py module.

[kelle]

when changing adopted, check the agreement between multiple measurements. Raise an error if they are more than 2*err different from each other (or something like that).