Arpespythontools

- implementation of a custom data loader (user request)
- fix: include max index in `plane_slice` and `line_profile`

- extend boundary while calculating convolution for `laplacian` and `2d-curvature`
- fix: include max array index in `crop_2d` output

- Multiprocessor implementation of `kconv3d`
- Extend boundaries while calculating convolution for Laplacian and 2D curvature. This produces the same shaped output array as the input array, no need to remove border artefacts.
- Run workflow tests on Python v3.11 (as well as v3.10)
- Other minor improvements

- fix: `load_ses_spectra` incorrectly omitted last character of lines in data block

- New `save_xps` module to save XPS data in two column format.

- Improvements to `load_ses_map` module.
- Few function and file names changed to all lowercase.
- Other minor changes.