Versioning issues in Policy Types

Known issues:

• When multiple versions of a policyType is created, we will be able to fetch only one(usually the latest one) from DB, other versions will give 404.
• When fetching policies, we also get the corresponding policyTypes now. This policyType can be of the wrong version(if multiple versions of a policyType exist,and the policies created are not of the latest version)
• If multiple versions of a policyType are available, and if this PolicyType becomes a parent PolicyType, then and we will not be able to fetch the child PolicyType or create policies against it. There is no way to specify derived_from_type_version.

In ToscaServiceTemplate, policyTypes is Map<String, ToscaPolicyType>, where for key string we are currently only considering name and not version. So, only one entry for policyType is allowed, other entries with other versions cannot be placed in the map.