These are implied values as they are the defaults in the XSD
for optional attributes/elements. However I've noticed that
I keep running into issues where Mac Excel/Word fail to open
a file unless an optional default is provided.
I'll just add them all to hopefully increase compatibility and
save painful file format debugging sessions later.
This seems like the better choice, a lot of the logic is shared
between the document types, and it allows generating filenames in
a single place.
The only downside is that you must pass in the document type as
some content types have different typical names depending on the
document type (e.g. an 'office document' is the main document.xml,
workbook.xml and presentation.xml
Decoding was getting fairly complicated, it seems cleaner
to have something handle the relationships file and traversal
and the document just be notified via callback when new
files have been found.
