Rework dynamic_reference management, introduce dynamic_reference_nocheck

Rework dynamic_reference management, introduce dynamic_reference_nocheck

New dynamic references are now resolved at construction and all of them are re-resolved when a relevant service is added or removed; resolution is no longer done in operator->

dynamic_reference_nocheck is a variant of dynamic_reference that does not check for value being null in operator-> / operator*
dynamic_reference still throws an exception when used in this case

Both kinds of dynamic references support .check(): an exception is thrown if this is called when value is null