Task space feature

This PR continues PR #210 but with the source moved into the simbody/simbody repo from chrisdembia/simbody. (via short-lived PR #237). This is so Chris and I can work on it together and with osrf.

cc/ @chrisdembia @hsu @scpeters 
Maybe some of this comment should go at the top of this document? Example-writers may not read this far down.