Support duck type from spec

[arthurdm]

The Service Binding Specification introduces a duck type for provisioned services to make themselves bindable.

To support the desire of being spec compliant, this issue should enhance SBO to support this pattern for target services.

[sbose78]

Thanks.

[sbose78]

@pedjak could you schedule this for a design review please with the team? I've tentatively marked this for 0.4 ( cc @baijum )