generate list of data files on the fly

Summary:
the previous list was woefully insufficent and not including half the
things necessary for generating a working apidoc from the installed
kapidox (css, 3drdparty etc. were missing)

Test Plan: installing and then using kapidox_generate actually generates fully themed docs

Reviewers: ochurlaud

Reviewed By: ochurlaud

Subscribers: kde-frameworks-devel, kde-doc-english

Tags: Frameworks, Documentation

Differential Revision: https://phabricator.kde.org/D22421