One parent should be treated as canonical

[ghost]

Categories with only one parent should be treated as canonical and given a page with parentcategory/category with the parentcategory hyperlinked in the header.

[ghost]

proposed model: If a dirname exists, it's the category's dirname. Else if one parent exists, then its the dirname. Otherwise, no dirname

if a dirname exists, there must also exist a category of the same name and all users of the dirname are implicitly children of the associated category

[setr]

same as #11