Handle long file names

[mhucka]

We have run into a situation where an EPrints server returned a file name that is longer than the allowable file name length for a given file system. This leads to a failure when attempting to write the file during the creation of a bag. It's not clear what can be done about this, however. The file name portion of the URL is often not easily segmented into a better file name, and even if it was, then the file name on disk would differ from the file name in the EPrints record.

Needs further thought and engineering.