Adds logic layer for handling plans and roles

Adds the logic for handling the interactions between the storage layer
and the template combination functionality. This layer will be called
by the REST API to do the actual Tuskar functionality.

Change-Id: I0795d96a4f4f5c4309dde3c45fd6958431b65c0b
Implements: blueprint tripleo-juno-tuskar-plan-rest-api
Merge "Adds logic layer for handling plans and roles"