Add doxygen API docs to the website

Add gh-pages to forked repo:
$ git checkout upstream/gh-pages -b gh-pages
$ git push -u origin gh-pages

Generate new doxygen docs:
git checkout master
ant clean
ant docs
rm -rf gen/doxygen/latex/
git checkout  gh-pages
rm -rf pages/doxygen/
mkdir -p pages/doxygen
mv gen/doxygen/html/* pages/doxygen/
git add .
git commit -m message