Add legacy MD5 Minter

Submitting this for discussion.

Interested in ideas about more robust testing of edge cases for existing ID's. This needs to be able to replicate https://github.com/dpla/ingestion/blob/develop/lib/akamod/select-id.py#L55
As I mentioned in person, the Primo collection ID creation code is a little different: https://github.com/dpla/ingestion/blob/develop/lib/fetchers/primo_fetcher.py#L68-L81

There are two issues I see here: differences in normalizing spaces to two underscores vs one (for the Primo collections), and ensuring that the title data in Primo collections is UTF-8 encoded before the MD5 gets calculated.