Consistently document default and example values

Previously, the "Common application properties" appendix had no
consistent use of a configuration key value. It could just as well be
the default value or an example.

We now always document the default value after the "=" sign and
eventually add an example with the phrasing "For instance".

The keys have also been reordered so that they follow a natural (i.e.
lexical) order.

Closes gh-3230
Closes gh-3160
Closes gh-3155
Closes gh-3153