Create tool to auto-populate documentation examples for decision point objects

[ahouseholder]

This is (I think) the last item to cover the changes that were all bunched up in #339.

This issue is to create a tool that can automatically populate example text (markdown), json, and possibly python examples based on python SsvcDecisionPoint objects. The target is to be able to automatically generate these as separate files that can be included into the info box at the top of the page for a decision point, as for example in:

https://certcc.github.io/SSVC-staging/reference/decision_points/automatable/

(screenshot follows)

The resulting output should be clearly delineated as generated content to reduce the chance of misplaced effort in manually editing docs that will be overwritten by a future build process. (I.e., use a specific directory name and/or comments in the files to indicate that they are generated files and should not be edited.)