Create upload method for References

[RWShelton]

We need to be able to upload the Reference file specified in the loader document according to our new upload process. Note: The reference loader schema is slightly different than the ERD tables. We made some simplifications to the fields of the tables we are actually exposing to users via upload/read.

[RWShelton]

This has a dependency on a change made on the plot observation update - references have no foreign keys so it needs the optional validate step created on that PR.