Add a 3scale addon

[nicolaferraro]

It would be nice to provide an addon that adds some annotations that allow an API manager like 3scale to discover the service created by camel k.

The addon can be disabled by default and, if enabled, it can add e.g. the following annotations to the service:

• "discovery.3scale.net/scheme" (required): "http" (customizable, but probably fixed)
• "discovery.3scale.net/port" (required): "80" (by default, it's the service port, not the container port, customizable)
• "discovery.3scale.net/path": the root path, if provided in trait customization
• "discovery.3scale.net/description-path": "/openapi.json" (or the path to the openapi spec if available, customizable)

And label:

• "discovery.3scale.net" (required): "true"