Allow multiple versions of entities to be returned

Fix .gitreviw file to point at "master" rather than "dublin"

Allow return of multiple versions of policy types and data types in
TOSCA service templates and multiple policies in TOSCA topology
templates.

Because the return type is a list of singleton maps, utility methods
were added to return flat maps of poliicy types, data types, and
policies keyed by a compound ToscaEntityKey name/version key.

Issue-ID: POLICY-1807
Change-Id: I355038aaca26f41064d0e3cb3b45b1de2294cf5f
Signed-off-by: liamfallon <liam.fallon@est.tech>