Better debug message

git-svn-id: https://svn.forgerock.org/openig/trunk@675 dbb9e58e-28e6-4ce0-90e8-f11d9605b710
Make documentation described constraints backed by code constructs:
* `preparedStatement` attribute is required
* `parameters` could be optional if no placeholders are specified

Used the as-list-of construct to init the parameters' expression's value.
Synched the doc

git-svn-id: https://svn.forgerock.org/openig/trunk@676 dbb9e58e-28e6-4ce0-90e8-f11d9605b710