An attempt at better documentation for q-d

[abailly-iohk]

This PR contains 2 things (which should probably be separated), and is in draft because it's lacking a 3rd thing:

1. A q-d implementation of the Circular Buffer example which is comes from the Pulse article and is also implemented in q-s-m. This example could be a good basis to explain and test parallel actions from First draft of parallel state machines #72
2. An attempt at explaining what is Dynamic Logic and why it's important and useful
3. A way to generate and publish these as documentation on this project's pages: https://input-output-hk.github.io/quickcheck-dynamic

Checklist:

• Check source-code formatting is consistent