Automatic resolution of storage type

/cc @kamsi

Currently when we want to get given value we need to specify which storage we use direct, computed or reduced, but after some improvements engine may intelligently resolve out of provided id (or path) which storage handles given value.

For now wether query is about computed path can be resolved from registered indexes, for reduced path tracking will have to be improved as custom reducers are not marked internally.

Additionally it would be good store persistently somewhere all initialized indexes. Currently indexes are known only known from loaded programmatical configuration.
If given index is initialized in some other previous setup, engine will not be aware that such index were handled.