Clear the page for each configuration options similar to the directives.
Use a rubric instead of a definition list for the application
configuration options similar to the directive documentation pages. For
direcives and application configuration options use the same rubric
order.
Generalize value constraints to constraints.
This patch does not change hand written content.
If only one constraint is present, then use a single sentence, otherwise
use a list for the constraints. Format the constraints so that the line
length limit is maintained.
Try to bring all descriptions up to date. Add cross-references to
several options. Clarify configuration value constraints.
Use this template also for initializer type options.
Close#3901.
