Merge pull request #6878 from miri64/doc/enh/beatify

doc/doxygen/footer.html

doc/doxygen/header.html

doc/doxygen/riot.doxyfile

doc/doxygen/src/config.json

doc/doxygen/src/css/bootstrap.min.css

doc/doxygen/src/css/fonts.css

doc/doxygen/src/css/riot.css

doc/doxygen/src/fonts/glyphicons-halflings-regular.eot

doc/doxygen/src/fonts/glyphicons-halflings-regular.svg

doc/doxygen/src/fonts/glyphicons-halflings-regular.ttf

doc/doxygen/src/fonts/glyphicons-halflings-regular.woff

doc/doxygen/src/fonts/glyphicons-halflings-regular.woff2

doc/doxygen/src/fonts/miso.eot

doc/doxygen/src/fonts/miso.svg

doc/doxygen/src/fonts/miso.ttf

doc/doxygen/src/fonts/miso.woff

doc/doxygen/src/js/bootstrap.min.js

doc/doxygen/src/js/doxy-jquery.js

doc/doxygen/src/js/jquery-ui.min.js

doc/doxygen/src/js/jquery.min.js