Milestone 2 simulation upgrade

Motivation

The requirements of milestone 2

Changes

• Added a simulation of the robot arm and attached it to our little simulated Munna
• Made a control wrapper to control the arm in simulation similar to how you control it in the real world. It uses the same topic and message type as the real world one. Topic is /joint_trajectory_point of type std_msgs/Float64MultiArray. Refer to the RSS website to see how to control it - http://wcms.inf.ed.ac.uk/ipab/rss/practicals/getting-started
• Made simple models for the button, boxes and rocks for Milestone 2
• Added said models to the simulation so that we can interact with them. NB. the button is a static fixed box and not actually a pressable button
• Made the model of the world more cardboard-y

Testing

• In simulation using manual controls for the arm. Pretty accurate to the real world (including speed). Worth noting that it's not exactly the same though.
• Interacted with all new objects in the simulation and picked one up manually with the arm.