Reusable queries

[snikolayev]

Need ability to create reusable abstractions (such as queries) that can then be used in many rules as building blocks w/o having to repeat the logic.
This should play nicely with forward chaining (i.e. reactive queries), and, in the future, backward chaining (lazy queries).

[jameshulse]

Hi @snikolayev, you mentioned this over in Gitter and I would be happy to help you implement this if you have some ideas of where to begin.