docs: document surface calibration

[JoepVanlier]

Why this (work in progress) PR?
Currently, users cannot reproduce the full surface calibration workflow.

This worked example will allow them to do so, and hopefully see the advantage active calibration brings in that situation.
Docs build here.

A few open questions I still have with this:

• Touchdown seems to result in a bias of approx 100 nm here.
• The focal shift seems to be around 0.91 for a water objective, which seems low? I would expect this closer to unity.

Edit: Based on Aafke's suggestion I have moved the notebook to the fundamentals section, as it is indeed more related to demonstrating some effects rather than an actual worked example.

[aafkevandenberg]

Hi Joep, this is super nice, this will be very useful.

I have to read this a couple of times to understand the details. But as a very general initial feedback I would say to splits this notebook in 2:

1. First just list the steps that a user has to take to start using the activate calibration, in exactly the right order. So, somebody who downloads the notebook just can load his/her own data and quickly go through the steps. (And, link to the page on the pylake docs that explains how to recalibrate the force using the obtained stiffness)
2. The second part of the docs can explain the background and the mechanisms that are taken into account, and how active and passive calibration are compared.

[aafkevandenberg]

Here it would be helpful to add labels 'active calibration' and 'passive calibration' and a legend

[JoepVanlier]

Hi Joep, this is super nice, this will be very useful.

I have to read this a couple of times to understand the details. But as a very general initial feedback I would say to splits this notebook in 2:

1. First just list the steps that a user has to take to start using the activate calibration, in exactly the right order. So, somebody who downloads the notebook just can load his/her own data and quickly go through the steps. (And, link to the page on the pylake docs that explains how to recalibrate the force using the obtained stiffness)

2. The second part of the docs can explain the background and the mechanisms that are taken into account, and how active and passive calibration are compared.

Ah yes, 1 is part of the force calibration docs reshuffle. I spun this off from that branch, since the size of it was getting out of hand. This PR really only addresses point 2 for one more advanced use case (surface calibration).

edit: after discussing, it may be a good idea to move this entire notebook to the fundamentals section, as it contains a lot of detail that a typical use case probably doesn't require