Collection filter syntax

[beikov]

Add support for the bracket notation to filter collections. Within the brackets, an implicit variable _ exists (that can be omitted) to access the current collection element for the filtering. A possible example is priceHistory[price < 10 and date > TIMESTAMP 2020-01-01] is not empty. Collection filtering produces a collection again. The filtering should only be possible when the DomainOperator is enabled for the collection type. The interpretation implementation is straight forward. The persistence implementation requires help from the developer as that is dependent on the backing storage. We could try to attach support metadata on the collection types.