JSON query support

[btrask]

Right now we have the "user query parser" which handles common high level query syntax (like Google). We also have a JSON query parser but it's sort of outdated and bad. Doing this properly is critical for other applications to be able to use StrongLink as a back-end.

In particular one feature we need is a user query element that can be embedded in a JSON query so that user queries can be combined without worrying about validation or whatever.