Create custom environments with JSONs

[chalo2000]

In version 3 of the simulator we want to be able to create different environments to complete different tasks. We'll do this with a JSON format that makes it easy to specify what objects are in the environment (and where they're located for the renderer). For robustness, we'd like to eventually be able to procedurally generate these environments such that they contain the minimum objects to complete a certain task but may contain various more as noise.