OAK-702: Optimize access to node type information

Remove another getDefinition() signature from DefinitionProvider.
No need to check for previous single/multi-valuedness of the property
anymore in AuthorizablePropertiesImpl.

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1461107 13f79535-47bb-0310-9956-ffa450edef68