SiSU 4.1.12

* ocn (object numbering) on, off, text block using "--~#" "---#" "--+#"
* grouped text, open, close of blocks using tics "```"

* e.g.
  open code block:  "``` code"
  close code block: "```"
  start poem:       "``` poem"
  end poem:         "```"
* remove need for an empty line between opening & closing of a text block

* switch ocn off & on for a block of content, line containing only
  off: "--~#" (omit headings where possible) "---#" on: "--+#"