Add humanoid LQR to documentation and document row/column major

[nic-barbara]

The humanoid LQR example should be written up much the same as the cart-pole example. This will also involve:

• [x] Revise documentation on row vs. column major arrays following the changes in this pull request.
• [x] Update cart-pole example script and docs
• [x] Write up humanoid LQR example, referencing and following the DeepMind colab notebook