Improve handling of multiple policy in APEX PDP

As a ONAP developer, I would like to improve the handling of multiple policy in APEX PDP.

Currently all the Tosca Policies are merged together and deployed in the PDP. That solution brings a lot of complexity in terms of handling duplicate names, tasks etc. Moreover the chances of problem with one policy impacting others.

Proposed solution is to start one instance of the inner engine (ApexMain) per Tosca Policy. Thereby making the multiple policies independent.

It will either fix or minimize the impact of following:

• "name" field in apex config must be same for all policies.
• Concepts must be unique across multiple policies.
• If one policy is messed up (example - JSON.stringify issue) then whole engine is affected thereby failing all other policies which are already deployed.
• Graceful shutdown of policies during policy undeployment.
• Improve stability of APEX engine and multiple policies deployment