Improve documentation of joint dof mapping, common use cases for articulation handling

[eric-heiden]

Many people run into issues related to getting the right joint limits, position coordinates, and other dofs for a particular joint.
We should improve the documentation we have on this: https://newton-physics.github.io/newton/concepts/articulations.html#definition-of-joint-q
Perhaps some common real-world examples would help:

• How to set joint_q to values centered at the joint limits? Note here we need to skip free and ball joints to not set quaternions to strange values.
• How to move articulations? Easy for floating-base, but for fixed base you need to set joint_X_p. Better to use ArticulationView for this.
• How to use ArticulationView?