Update sphinx templates

In #584 Radu pointed out that a slightly different set of templates/styles are used on doc server to generate tutorials:

> Wait, I think the problem is that we have different configuration files for Sphinx on docs. I believe they are here: pointclouds.org/sphinx-tutorial-templates.tgz (no worries, i'll erase later).

This pull request updates layout file and adds CSS files so that what we have in Git match the archive contents. However, it does not touch the 'conf.py' file, where file suffix remains "html". In order to change it to "php", a CMake variable introduced by #729 should be used.