Remove Target and TargetType

The dependency should have been removed in the last review to
remove SDC and policy-yaml legacy code.

It was revealed that usage of TargetType and Type were spread out over the
actor code. Those fields are represented differently in the new
TOSCA Operational Policy Type, so fields were created to capture
those values to be used by actor code.

Issue-ID: POLICY-2428
Change-Id: Ib783526a518ca7942ae9e38019bd343639f4dd98
Signed-off-by: Pamela Dragosh <pdragosh@research.att.com>