doc: added Doxygen layout file.
doc: added Doxygen layout file.

Will be used to tweak the documentation output even more.

MiUishadow/magnum,DerThorsten/magnum,DerThorsten/magnum,ashimidashajia/magnum,MiUishadow/magnum,DerThorsten/magnum,ashimidashajia/magnum,ashimidashajia/magnum,MiUishadow/magnum,MiUishadow/magnum,ashimidashajia/magnum,MiUishadow/magnum,DerThorsten/magnum,MiUishadow/magnum,ashimidashajia/magnum,DerThorsten/magnum