Maintenance simplify tools and usage for editors

[sthagen]

• We should derive all section and example mappings from the sources per a sections tool and configuration (only source edits, no more json mapping files juggling)
• We should merge the volatile (html, gfm-plus) and lapidify (pdf) processors into one assemble tool (less maintenance cost)
• We should have some support for missing or duplicated example numbers during derivation (faster fixes)
• Configurations for section ref display style allow us to adapt to future needs more easily (like prefixing with a section-sign or by amending with a section title text part)
• We may want to have a make clone-info command at hand to expose the branch-commit- and node-identifier
• We want make clean to also remove typical python runtime ephemerals

[LisaBobbitt]

Agree with Stefan on this.