Adding NgIoh, update doc, reduce dependencies, fixing various bugs, more plotting.

What's Changed

• reduce compulsory dependencies by @bottler in #1552
• Update machinelearning.rst by @teytaud in #1553
• fix ngoptrw by @teytaud in #1555
• Update base.py for better constrained optimization. by @teytaud in #1554
• fix deprecation warning by @teytaud in #1556
• NgIoh variants by @teytaud in #1551

Full Changelog: 0.12.0...0.13.0