DynamicsBackend tutorial

[DanPuzzuoli]

Summary

Closes #192

This tutorial is written to show users how they can use the DynamicsBackend to specify pulse-level simulations in various ways:

• Running simulations directly specified as pulse schedules
• Running simulations specified as circuits, but where each element either has an attached calibration, or a corresponding pulse definition in the target
• Simulating processes in calibration and characterization experiments generated by qiskit-experiments

Each of the above requires different levels of configuration of the various attributes of DynamicsBackend, so this tutorial will guide users on the setup necessary to achieve their desired task.

Details and comments

It is currently just a jupyter notebook in the docs/tutorial folder.

[DanPuzzuoli]

I've just converted to RST. I've added pandas to requirements-dev.txt, but it's only used for table visualization, so it may make sense to remove this.

[DanPuzzuoli]

@coruscating In addition to the above replies, with the addition of cross-linking of qiskit_experiments, I've tried to get all class references to Terra and Experiments to be proper links (hopefully not missing any).