Set Frame for Revolute/Prismatic Joints

[dmklee]

I would like to create joints where the joint frame is translated and rotated w.r.t. the parent body frame. Similar to how joints can be defined in a URDF.

Fixed joints already allow this, and this PR extends the capability for spherical joints in rust. I tried modifying Generic Joint to accept arguments for frame1 and frame2 but I was not able to get it to work. I believe this snippet of code automatically converts generic joints to prismatic/revolute/etc based on the locked axes, so the resulting joint doesnt end up using the frames I specified.

There is a similar request to allow for different axis in this issue.