Refactor/clean the xml

[stimpfli]

• Explore the usage of multi dog joints
• Clarify the relationship between dof sequence and inverse kinematics:
  • Either make it flexible to using any sequence
  • Or write script to change the order
• Remove actuators and cameras and initialise them in init()
• Check that simulation parameters are fully relevant
• Check that body, joint, inertial and geom parameters make sense