Disable --match-by-site

[abostroem]

The pipeline currently allows the user to use standards taken at the same site but with a different instrument if the user passes in the --match-by-site keyword. This is never right. We should remove this option and update the manual. If there is a lack of standards to build a Landolt catalog we can always obtain them after the fact (we just need a photometric night of data of the SN field and standard field to build the catalog - this isn't time sensitive).