Phase partials needs a tutorial

[briantoby]

The naming is a bit obscure and use is a bit complex. A tutorial would help.

Compute “phase partials”:

• Click on the main entry for a histogram and use “Phase partials config”

• Then run a refinement to compute the partials.

• Use the “p” key in the plot to see the contributions.

• Also note the “Save partials…” command