Blender Git Loki

New python submodule `mathutils.interpolate` for various mesh interpolation and weighting methods.

This module will contain mirrored functions for calculating and applying
weights for points on a mesh. This includes barycentric and UV weighting
and possibly more advanced global weighting such as harmonic weights.

The naming should follow this scheme:
<type>_{2d,3d}_{calc,apply}

e.g.
poly_2d_calc
poly_2d_apply
uv_3d_calc
...

Reviewers: campbellbarton

Differential Revision: https://developer.blender.org/D939