API Operator to simplify API lifecycle management

The idea behind the API operator is to offer full control of the API lifecycle by simplifying operation and management.

The initial version of the API operator aims to make it easier to synchronize changes between your APIs and its presence in 3scale (integration, access, mapping rules, etc.), simplifying and automating deployment to multiple environments. It should cover requests such as https://issues.jboss.org/browse/THREESCALE-1187

In order to achieve that, we're adopting an API first approach using OpenAPI spec as a unique source of truth, which is a pre-requisite (apart from 3scale and OCP).

Product doc with detailed use cases can be found here
https://docs.google.com/document/d/1UYS5VB8mJVcMkm2om6hVtq1r7fucqZEdT3ew3S4QTw8/edit#

Deliverables: CRD.

We aim to release the API operator with 3scale 2.5 as a Technological Preview.