NEW FEATURE: Allow to add formatoption presets

Summary

It should be able to import/export presets, i.e. YAML-formatted mappings from formatoption key to value

Reason

This allows to customize the plot easily for recurring tasks or data files.

Detailed explanation

A preset file should look like

title: "{desc}"
mapplot:
  projection: "ortho"
lineplot:
  color: "k"