Nanite

- docs: preprocessing methods not correctly rendered

- fix: make sure that AFM metadata contain the spring constant and
raise a MissingMetaDataError if this is not the case
- ref: deprecate `IndentationPreprocessor` class in favor of a more
flat submodule (17)

- docs: add POC table to docs

- fix: do not modify preprocessing options when applying them (create
a copy of the dictionary)
- ref: remove `Indentation.reset` in favor of `AFMData.reset_data`

- feat: new contact point estimation method "fit_constant_polynomial"
which applies a piece-wise constant and polynomial fit
- feat: contact point estimation methods now return detailed
information about the procedure (currently plottable data to
understand the process)
- fix: spatial smoothing not working in some cases (15)
- enh: add `steps_optional` in preprocessing to allow fine-grained
control about order of application
- ref: remove "...smoothed" column data (which was never used anyway);
instead, apply smoothing directly to AFMData subclass
- ref: rename `require_steps` to `steps_required` in preprocessing
decorator
- setup: bump afmformats from 0.16.0 to 0.16.4

- 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