Currently,  the option to add directives to a topology template is only implemented for Service Proxy with this user story implementation the same action will be enabled for selected VFC on a VF composition.

Motivation:

Tosca simple yaml profile allows for directives to be specified for a node template to provide processing instructions to the orchestrator. 
There is already support for this in SDC UI in service design and also in the SDC backend. This change seeks to broaden that support to allow users to use this feature in VF design so as instructions can be added for the orchestrator on resolving node_template implementations for orchestrators that can support such instructions.

For example the following extract from a VF template shows two VDU instances whose 'host' requirement is met by the same instance of org.openecomp.resource.VFC.MyCompute. The presence of the 'select' directive in 'myCompute 0' informs the orchestrator that this node is abstract and it should find an implementation for it from its inventory.