changed character set to UTF-8 to present unicode strings in a proper way

in DTML. This is a workaround because usually conversions should work
*without* importing the codecs module explictly

      - Collector #227: improved handling of unicode string in TextIndex.py
        with unmodified default encoding in site.py.

(Collector #221)

        replaced by underscores to avoid confusion with some FTP clients.

Use difflib instead of ndiff (http://collector.zope.org/Zope/32)

        because the downloaded file has been stored with a HTTP
        header at the beginning of the file. Fixed!

        an incomplete filter based on interfaces.

trunk.  I'm *almost* done with the merge; the only file not yet merged
is FileStorage.py.

        <h0> tags.

Fixed tests. They were comparing DateTimes which had been created at different 'resolutions' causing random but frequent failures on Windows.
Now comparing repr()'s of the DateTimes which gives just teh right level of precision.

Slightly better error reporting. Dunno why this test is failign on windows, it appears to be loosing thingthe 'decl' and 'doctype' events at the very least :-(

Fixed line ending problems causing test failure. Binary mode not appropriate as CVS checks otu with different line endings depending on the OS.