Switched to ARC and began preparatory work to solve #2.

In particular, the table making is now factored out, and classes for
ZIP files and WordprocessingML files are now added.
Convert all code to use TableDocument.

That way it will be easier to add Office Open XML, and possibly ODF, later.
Export files as docx

This fixes #2. It required quite a bit of refactoring at different places.
Include empty row before every new letter (can be turned off).

This fixes #3.
Forgetten project.pbxproj changes

Xcode didn't tell me about them.