Fix a comment in NaturalTransformation

Reported By: Andrej Bauer
Duals -> Dual

For consistency with the singular of [Category], [Functor], etc.

Reported By: Andrej Bauer
Solve trivial obligations after [path_functor]
Port subcategories
Fix ambiguious and incorrect references
Make symlinks to wrapper scripts work

If you symlink to the hoq* scripts, the symlinks didn't work.  Now they
should; we need to recursively resolve symlinks before taking the directory
name.

Reported By: Thomas Braibant
Merge pull request #234 from JasonGross/wrapper-scripts-symlinks

Make symlinks to wrapper scripts work
Merge pull request #227 from JasonGross/categories3

Port subcategories