More natural configuration of object streams

/cc @kamsi

Currently when we want to configure some action on when given object receives certain state, we usually build collection as e.g.

db.BusinessProcess.filterByKey('isRevisionReady', true).on(function (event) { ... });

What's painful is that usually we rewrite similar event handler which works around add, delete, batch events. It might be nicer if we can achieve same via something as:

db.BusinessProcess.stream('isRevisionReady', true).on(function (businessProcess) { .. });

This stream will also at initialization stream all objects that already match expected state.

Additional functionality would be to create a streams that are also guarded by pre-triggers, so we observe specific state change from A to B, and not just fact that object landed at given state.
Very rough idea, on how it may look:

db.BusinessProcess.stream('isRevisionReady', true)
  .to('isRevisionApproved', true).on(function (businessProcess) { .. });