xhtml11.css

- apps/utils/nxdoc: Created a first version of a command-line script around the nxdoc machinery, for Makefile integration. - Makefile.in: Added two experimental nxdoc make-targets: [make yuidoc] and [make xowiki]. In addition, provided for a doc-specific cleanup target: [make cleandoc]. Also changed the way TCLLIBPATH is initialised for makefile runs, to preserve the surrounding environment settings. - tests/doc.test: Deactivated obsolete sections; actual cleanup is pending. - Refactored nxdoc code fragments into sub-packages, namely the html and xowiki rendering components; renamed some file and directory. - Some necessary adjustments to make nxdoc work with the new property/variable nomenclature; spotted some misbehaviour of [namespace import] when running under 8.6b2 (to be investigated; see XOTcl-lanfRef.xotcl)