normalized some URIs and added glob support to fileset-filter hrefs

# px:fileset-add-entry
- normalized input href
- if the file already exists in the fileset; delete the existing entry

# px:fileset-filter
- support for the glob characters * and ? in the href option

# px:fileset-load
- normalized base URIs of in-memory documents

# mediatype-utils
- removed a log statement
px:fileset-add-entry: preserve existing instead of new entry

also fixed a bug in px:fileset-filter (did not pass the tests)
Merge pull request #21 from daisy-consortium/uri-normalization

fileset-utils: normalized some URIs and added glob support to fileset-filter hrefs