387 increase plug in manager functionalities

[gregLibert]

No description provided.

[gregLibert]

Can be tested using the plugin-manager postman collection.

Note: The new version of the plugin manager doesn't replace the previous one. It's a side service right now.

[gregLibert]

This PR is huge, sorry about that.
To easier the code review load you can consider this as a meta PR with:

• some cleaning before starting the job
• API endpoints creation: just focus on the swagger file. All the rest is automatically generated code.
• plugin and plugin manager object
• linking plugin adn plugin manager with the API endpoints
• passing the instantiate manager as an external dependency instead of having a global variable - (bad boy!)
• a little postman to test it
• all the rest is cleaning stuff

[SebastienValla]

nice !