Normalize the uniqueFooIdentifier() functions

[nexushoratio]

A bit all over the place.

• We should figure out if using if (element) {...} defensively, or not
• Probably always start with let content = element.innerText;, then fine tune
• Normalize name if always include associated Scroller (or Shared in the exceptional case of Feed)
• Use of Logger as this will always refer to the Scroller this here (no need to use the global)
  • Always intro/outro for element/content
  • Experiment: Can const me = Class.method.name work, instead of strings (something recently used in an unrelated Apps Script)
• Document above in STYLE-GUIDE