Nanite

- BREAKING CHANGE: The contact point estimation method "scheme_2020"
has been removed, although it has been the default for some time.
It turns out that it does not perform so well and there are other
more stable methods (to be implemented). Furthermore, some of the
contact point estimation methods were improved so that basically
many tests had to be updated. This will not break your analysis,
it just means your contact points will change.
- feat: implement options for preprocessing methods
- feat: the "correct_tip_offset" preprocessing method now
accepts the "method" argument (see new poc submodule)
- fix: contact point estimation with gradient-based method
"poc_gradient_zero_crossing" did not really work
- enh: improve contact point estimation with "fit_constant_line"
- enh: speed-up contact point estimation with "deviation_from_baseline"
- ref: CLI profiles now use JSON format by default
(old format still supported)
- ref: move contact point estimation to new 'poc' submodule

- enh: implement 'require_steps' in preprocessing to make sure
that steps are executed in the correct order
- enh: add several helper functions for preprocessing

- BREAKING CHANGE: segment in FitProperties is now an integer
- setup: bump afmformats from 0.15.0 to 0.16.0
- docs: update doc strings for the "sneddon_spher_approx" model
- docs: remove duplcate docs for model functions

- ref: introduce preprocessing_step decorator for managing
preprocessing steps
- ref: explicitly request "force-distance" data from afmformats
(can be lifted by ``setting nanite.read.DEFAULT_MODALITY`` to ``None``)
- setup: bump afmformats from 0.14.3 to 0.15.0 (initial support for
loading creep-compliance data)

- docs: fix build

- setup: bump afmformats from 0.14.1 to 0.14.3 (adjust tests, speed)