Typo in comment.
Revert "Typo in comment."

This reverts commit 507ce9a167a2b6b1ff83107510b4e87a995c4963.
Hide unsupported Body::Particle from Doxygen.
Merge branch 'rigidContactSandbox' of https://github.com/tkuchida/simbody into tkuchida-rigidContactSandbox
Merge branch 'master' of https://github.com/simbody/simbody