Align concave polygon normals with boundary winding

[ArianMoeini]

Summary

• Use the full polygon boundary to orient its best-fit plane.
• Fix concave polygons whose first edge makes the old centroid triangle point against the polygon winding.
• Cover every starting vertex and both winding directions in a regression test.

Closes #1487.

Tests

• PYTHONPATH=src:/private/tmp/compas-test-deps python -m pytest tests/compas/geometry/test_polygon.py -q — 15 passed.
• git diff --check — passed.