Sidpy

Minor release. Small fixes to image windowing, four dimensional visualizer, and adding of a structure attribute to the sidpy.dataset object.

Small update to sidpy. Changes since last version:

- Added CHANNEL dimension type for sidpy dimensions (for example of usage see this [link](https://github.com/pycroscopy/pycroscopy/issues/273#issuecomment-1267480139)) . This is useful for multi-channel spectral datasets, which can now be plotted using the intrinsic .plot() method
- Added updated capability on spectral visualizer to enable plotting of multi-channel spectra
- Small changes with set_dimension() method to be more robust
- Minor bug fixes
- Updates to various tests

This release adds a few 'under the hood' changes to the sidpy dataset object, with respect to chunking and folding/unfolding. Some minor edits to some visualization functions were also made. A new method `visualize_fit_results()` to the `SidFitter` class was added to aid in visualization of functional fits.

Added fitter class and improved tests.

Minor bug fixes
Support of thumbnails for icon view of directory