Section Number and Name:
Operator-SDK documentation. Related to Helm-operators

Describe the issue: 
The following behavior in helm operator project needs to be mentioned in documentation:
While scaffolding a new project, the helm operator scaffolder tries to use the cluster config for the best information. The permissions scaffolded in roles/rbac.yaml is based on whether the cluster config can be found or not.

While scaffolding a helm based project, `operator-sdk create api` needs to have a KUBECONFIG present. If not, users will have to add the required permissions for serviceaccount (in rbac/roles.yaml) manually. 

For example:
```
- apiGroups:
  - demo.my.domain
  resources:
  - nginxes
  - nginxes/status
  - nginxes/finalizers
  verbs:
  - create
  - delete
  - get
  - list
  - patch
  - update
  - watch
- verbs:
  - "*"
  apiGroups:
  - ""
  resources:
  - "serviceaccounts"
  - "services"
- verbs:
  - "*"
  apiGroups:
  - "apps"
  resources:
  - "deployments"

```


Additional information: 
The OCP documentation should point out the behavior of helm operator scaffolder to reduce confusions related to scaffolding of roles.yaml in the project.

cc: Alex Dellapenta (alexd)