Add community Eclipse Che operator (for downstream operators)

[davidfestal]

This PR is a followup of PR #280 that only focuses on the community-operators addition, as requested by comment #280 (comment)

This PR adds Eclipse Che operator to community operators. Eclipse Che operator auto-detects infra, so can run on vanilla k8s and OpenShift.

Tested on 4.0.0-0.9

[davidfestal]

There was still one unanswered question in the previous PR (superseded by this one): #280 (comment)

To summarize:

One of the possible settings in a CheCluster CR, which is disabled by default is auth.openShiftoAuth to enable authenticating against the current Openshift OAuth server.
It requires additional cluster permissions.

As @dmesser suggested, there are 2 options here:

• Either we consider this use-case as a niche, rather rare, use-case: then we would let the end-user add the permissions manually, as it is currently done in this PR (and documented in the CSV description)
• Or we can consider this use-case as an important and rather standard one: then we would prefer adding these permissions directly in the CSV permissions section, even if these extended permissions are not required in any case.

@l0rd @slemeur @nickboldt wdyt ?

[l0rd]

@davidfestal for option 2 it's not clear what happens if the users doesn't change any config and try to deploy on plain k8s: is the operator going to fail or will it figure out that there is no OpenShift oAuth and adapt the deployment to the underlying infrastructure? If it fails I would rather go with option 1 because that's the community operator: most of the deployments will happen on plain k8s and the default configuration should reflect that (k8s first).

[davidfestal]

@l0rd This PR is for Openshift only. The corresponding PR for plain K8s doesn't even have the explanation about the additional requirements, because it has no sense.
As for how the che-operator code behaves when it is installed on plain K8s and the user enabled Openshift OAuth in the CR, I just tested and it seems it is simply ignored.

[dmesser]

@davidfestal Can you please rebase and squash your commits?

[openshift-ci-robot]

@davidfestal: The following test failed, say /retest to rerun them all:

Test name	Commit	Details	Rerun command
ci/prow/scorecard	50d008d	link	/test scorecard

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