docs/table: added documentation for XML reading

Documentation for *.filter methods

    - fixes #15

    - easier to reuse this list in other places now

    - default alpha=0.1, can set alpha=0 for no fill

    - run 'python setup.py port' to write Macports Portfile for the
      current distribution
    - port command executes sdist if required to generate distribution
      tar.gz file and determine checksum digests
    - all digests should probably be manually checked