docs

* NamedQuery
* Custom queries
* java code listings

(cherry picked from commit 57676a27cd6f8feec6d102028a6e8eb0066c7de7)

git-svn-id: https://svn.apache.org/repos/asf/cayenne/main/branches/STABLE-3.1@1447826 13f79535-47bb-0310-9956-ffa450edef68