Add microfilm information to records

[wlpotter]

Since we now have images of the table correlating shelf marks to the micro films, we can add this to the records in the additional/surrogates element. This would go at the top-level for multipart mss (cf. #1958 for a similar use for availability info).

Some of the examples for TEI surrogate provide an idno element, a date, etc. They also have a @gmd attribute for the "general material designation" of the surrogate.