Normalize heading angle into sine and cosine

[zhengzl18]

The heading angles in PartnerObs currently range from $-2\pi$ to $2\pi$ and are normalized by deviding $2\pi$. But we are expecting the same outputs when $\theta=\pi$ and $\theta=-\pi$, or when $\theta=2\pi$ and $\theta=0$, which may not be the case with this kind of normalization. Switching to the sine and cosine spaces may make it easier for the neural network to handle.

[eugenevinitsky]

Good point.

1. We should be normalizing between -pi and pi or 0 to 2pi but not -2pi to 2pi
2. Separately, sine and cosine spaces may just be a better representation anyways

[daphnecor]

Thanks @zhengzl18 for your comment. We will update the angles to be between -pi and pi when we update the data processing script & available data. It should be in by next week sometime.