doc: Add a link to the Wikipedia comparison of CardDAV implementations.

Signed-off-by: Alex Zepeda <alex@inferiorhumanorgans.com>
report: Update pre/postcondition support for addressbook-query.

- Client specified limits are now honored.
- More expressive error handling now implemented.

Signed-off-by: Alex Zepeda <alex@inferiorhumanorgans.com>