Add documentation for original metadata

See https://trac.openmicroscopy.org.uk/ome/ticket/4645

Each format should now have an original metadata page in ```docs/sphinx/formats/```, which is linked from the corresponding top-level format page.  Original metadata pages are generated using this command:

```cd components/autogen
ant -Dfilelist=/path/to/list/of/files gen-original-metadata-pages
```

In this PR, the pages were generated using ```/ome/team/mlinkert/list```, i.e. a list of the filesets in test_images_good.

/cc @hflynn