Add structure for mkdocs instead of Sphinx

[Dref360]

Summary:

Makes the documentation pretty! This is WIP as I would like for everyone to have a good look before merging.

This will break our website for a bit once it is merged.

Fixes #216

Features:

• Use mkdocs-material for look
• mkdocs-jupyter for jupyter notebook

no more rst, so it is easier to work on.

Checklist:

• [x] Your code is documented (To validate this, add your module to tests/documentation_test.py).
• [x] Your code is tested with unit tests.
• [x] You moved your Issue to the PR state.

[Dref360]

I found an issue where active_learning_process.ipynb generates a search map of 32Mb which kills the search bar. Investigating how to reduce the final animation size.

[Dref360]

Everything is setup! Could @GeorgePearse and @parmidaatg re-review and then we deploy?