Robot model improvements

[cpr-fer]

Some small issues with the current robot models and urdfs include:

• Rebel 6DOF Mesh for Joint 4 seems to have an offset from center
• Meshes lost their colours/graphics in the conversion process
• Robolink RL DP 5 Joint0Coll.dae is just a copy&paste of Joint0.dae, replace it with a primitive/low poly version?
• Set velocity and effort limits to better educated guesses

[padhupradheep]

Hey, if you are interested, we at Neobotix few years back created new mesh files for RLDP-5 with colors.

You can find them at https://github.com/neobotix/neo_mp_400/tree/base_with_igus_arm/robot_model/mp_400/meshes