Update endpoint documentation to feed Swagger

[raymer]

1) Add documentation to each controller action using the XML format. This allows us to use the Microsoft standard for documentation that also works with Swagger. https://github.com/domaindrivendev/Swashbuckle#including-xml-comments

2) Add service metadata https://github.com/domaindrivendev/Swashbuckle#additional-service-metadata

3) Look for ways to add an introduction to our API in the Swagger UI

4) Look for ways to test endpoints in groups / by controller in Swagger.

[rajeshpandalss]

I guess we can close this for now.