New formulas: Ogre3D library and tools

These formulas add the 3D graphics library Ogre ( http://ogre3d.org/ )

Currently ogre-tools is a separate formula, following the structure of the Debian packages for the same project: http://packages.debian.org/search?keywords=ogre&searchon=names&suite=stable&section=all

This may not be the best way to do it since it involves downloading and compiling OgreMain twice. I'm happy to change it if the Homebrew maintainers decide that the tools should be a switch on a single 'ogre' formula instead.