Nicer rendering for queries

[edubrovski]

Currently we don't do any formatting when rendering queries.

1. Let's use newlines and tabs to make queries more readable, e.g

{ $and:
    [
        {  "intField": { $eq: 3 } },
        { "stringField": { $ne: "some" } }
    ]
}

instead of

{ $and: [ { "intField": { $eq: 3 } }, { "stringField": { $ne: "some" } } ] }

2. Use a compiler flag to enable/disable AST printing; disable AST printing by default.

@oolong/maintainers