Make reference notebooks for all the funcs in tools

[jgostick]

These got put on the back burner during the "tidy docs" marathon since they are not top priority, but we should get to them eventually.

[jgostick]

If any users wish to contribute a notebook to this it would be really appreciated. The idea is to make a minimal example/demonstration of what each function does, and how each input argument works. Examples of the final result can be found on the current porespy website, like here. All these pages are generated from normal jupyter notebooks automatically.

The process works as follows:

1. Firstly "fork" the porespy repo to your own github account, and download the code to somewhere handy on your computer. You'll then create a new branch off of dev, and add your notebook there. To manage the source code and version control, I recommend "fork" or "gitkraken", which provides a gui to deal with the branches and commits.
2. Now, choose a function in the tools module. You can see what functions need an example by looking at ones we already have on the website
3. Once you have picked a function, you create a jupyter notebook in the examples folder of the repo (i.e here under examples\tools\reference. The idea of the 'reference' notebooks is to keep it minimal, so you'll generate a test image that is suitable for demonstrating the function. You'll also create subsections where each argument to the function is explained and demonstrated.
4. The formatting of this notebook should be done correctly to ensure it renders properly. So, for the top-level heading use a single # , put the title of the function inside back-ticks ` so it gets the 'console' font, and put the various arguments as second level headings with 2 ## as well as the back-ticks. For other conventions refer to the existing examples, like how to plot the figures using matplotlib.subplots, etc.
5. Once the example is done and looking good, you 'commit' the file using your git client, then 'push' it to your own github repo.
6. Lastly, you can make a "pull request" which is a way of asking us to pull your example notebook into the main porespy repo. There may be a bit of editing required on the notebook, but this is all managed and discussed in the comment thread of the PR.

Any help is appreciated.

[jgostick]

Many of these are done, so I'm closing.