Joint Position Control is too soft and unstable in simulation

[DouglasS]

As reported by @stgray in issue #39, when transitioning to Joint Position Control in SCS the robot falls over immediately.

The remedy for this is non-trivial and unfortunately we probably won't be able to address it before the finals. It requires a different set of joint gains from what runs on the real robot and a great deal of tuning.

As soon as the DRC is over this should be high priority. Adding this to the bug tracker now so we don't forget.

[DouglasS]

Confirmed by Sylvain as a real bug.