Revamp property description page

This PR:

* removes the names of pre-2.10 property names from the documentation,
* adds a note about fuzzy matching of properties and a list of all
  prefixes reserved by Log4j,
* splits the system properties into sections according to the component
  that they apply to,
* updates the description of configuration properties based on the way
  they are used in the current code.
4 files changed