Seach by uploaded file, option to select hashing algorithm

[thomasegense]

The current implementation uses SHA1 and adds it as a prefix, example:
sha1:HIZMJVJQWAIEA2S3CT57BBRUFJZYNXEA

This is how we heritrix calculates the hash in the setup we use at the Royal Danish Library.

So upload by file will not work if another hashing algorithm is used. (using the solr field 'hash')