cloud-server layer to extend jaxrs-server layer

cloud-server depends on cloud-profile although we want it to be an extension of jaxrs-server layer.

This fix an internal refactoring that doesn't change the capabilities provisioned by the cloud-server layer.

The benefit of this refactoring is that core layers datasources-web-server, jaxrs-server and cloud-server are designed the same way with consistent dependency tree. As an example, a provisioned cloud-server or jaxrs-server server with jpa excluded allows to use datasources support in both cases.

The change imply:

• Make jaxrs optional in jaxrs-server (was optional in cloud-profile).
• Make cloud-server to depend on jaxrs-server.
• Update community documentation.