DB and API support all types of virtual network objects that network templates support

DB scheme should provide an ability to use all types of virtual network objects which are supported via network template. So that network template can completely be loaded into DB and API for node interfaces will reflect contents of template. Double logic for working with virtual network objects in network manager and serializers can be removed then.
Note. API changes will be not backward-compatible (or some transformation to "old" format will be required but flexibility of configuration will be lost with such transformation). UI will have significant changes in part of node's interfaces to networks mapping.