Critical Description
The query engine currently only supports properties that are stored within a node. It doesn't currently support "pseudo-properties" that are provided by an index, for example jcr:score() and rep:excerpt().
To support such properties, I suggest to change the Cursor interface to return an "IndexRow" (a new class that can return such pseudo-properties as well as the path) instead of just the path.
This may also speed up queries that don't require to load the node itself (if access rights can be checked efficiently or don't need to be checked for a given query).
