[WIP] 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 
Yes, that makes sense. I didn't spot those functions during the crude cut&paste operation I used to make TaskSpace.cpp. I'll fix and make sure it works on Windows.