Suggestion to custom python modules/toolbox structure

I just pushed a suggestion for how to organize the custom modules / code snippets, which we will use in the notebooks. The names of the files are just placeholders to give an idea for the splits. I added an example function search_umap_parameters to the plotting tools, but this is just an example of how that might look.

I think the cool thing is that everyone can add new functions to the modules, and push without merge-conflicts - and you can use the tools directly after installation of the main package. Let's discuss if this is the way we want to do it!