Write a dedicated manual file with a list of standard use-cases

[novoid]

The README.org did get long. Tool integration was separated in 2018-04. However, there should be a dedicated manual with a chapter that lists typical use-cases such as:

• tag gardening scenarios
• CV explained
• "hidden" features explained (mutual exclusive tagging, tagging original files within links, ...)
• generating tagtrees and re-tagging
  • "foo" -> "bar"
  • fix singular to plural
  • find typos in tags
• and much more