Native dm_control locomotion assets and implementation

Models, textures, task definitions and preprocessed motion capture data:
Copyright The dm_control Authors, licensed under Apache License 2.0.
https://github.com/google-deepmind/dm_control/tree/1.0.44

LabMaze maze generator and texture assets:
Copyright The LabMaze Authors, licensed under Apache License 2.0.
https://github.com/google-deepmind/labmaze

The original motion capture database was created by Carnegie Mellon University.
It may be copied, modified and redistributed; see http://mocap.cs.cmu.edu/faqs.php.
The dm_control authors fitted this data to the CMU humanoid. This package
includes only CMU_077_02 from the 2019 dataset and the 36 WALK_TINY clips from
the 2020 dataset. The original float32 samples are preserved.

The cubic-spline terrain interpolation is derived from SciPy's BSD-licensed
ndimage implementation. See LICENSE.scipy.
