Changes

Summary

1. Added speaking (and unambigues) filenames. We use a transformed version of the title field plus the URI plus a content type specific extension. To remove the URI from the file name we would need to extract the filename policy and keep track of file names we already used to avoid duplicates.
2. Set zip entries' date to the object's last modified date
3. Added rewriting support to the ZIP export
4. Actually return a ZIP. This version does not have any fancy features yet, i.e. neither link rewriting nor cool file names
5. Added skeleton zip generator (doesn't generate actual zips yet)
6. Fixed tree building and filename generation
7. Improved mime.types parser RE. Previously, lines containing a comment at the end and lines starting with whitespace were not recognized.
8. Simple file name generation (URI + Extension)
9. Added TextGrid MIME types
10. toString methods for testing & debugging
11. Factory actually produces something
12. Eclipse/m2e: Ignore unknown execution
13. Added a representation for mapping MIME types to filename extensions.
14. Basic tree factory
15. Skeleton for infrastructure to collect aggregation trees