* doxy-header.wml is build according to selected wml-layout

* navigation is included in the doxygen html files
* doxygen module structure is defined by the ordering in
  doxygen/modules:
  these entries are created first, all others, as they are parsed
* updated dune-doxy.css to fit to the new doxy-header and to use a
  much definitions from dune.css as possible

[[Imported from SVN: r353]]