Support JsonCreator with delegating mode

[foal]

Support @JsonCreator which takes not a list of properties but a single bean as an argument:

@JsonCreator(mode = JsonCreator.Mode.DELEGATING)

From Java doc:

A mode that indicates that if the creator takes a single argument, the whole incoming data value is to be bound into the declared type of that argument; this "delegate" value is then passed as the argument to the creator.