Linter to capture operator semantic versions

[kensipe]

There is a check for semantic versions defined in the operator at the time of installation here:
https://github.com/kudobuilder/kudo/blob/master/pkg/kudoctl/util/kudo/kudo.go#L292-L295

However we shouldn't have an operator that has a semantic version issue in the repos. A new operator dev discovered this and was confused by the message Error: unable to parse operators kubernetes version: Invalid Semantic Version.

This requires 2 efforts:

1. The error message should be more clear that this is an issue with the format of the operator
2. we should add a linter for package verify that errors on this condition

[javajon]

A workaround is to add:

kubernetesVersion: 1.14.0

to the operator.yaml

apiVersion: kudo.dev/v1beta1
kudoVersion: 0.10.0
kubernetesVersion: 1.14.0
maintainers:

In KUDO version 0.10.0 without this workaround the error message is:

Error: unable to parse operators kubernetes version: Invalid Semantic Version

Suggestion for the error message, if it's still needed:

Error: Encountered "Invalid Semantic Version". The value for the Kubernetes version (kubernetesVersion) in the operator declaration was not parsable. It's either missing/blank or this string "?" does not appear in the Semantic Version form (semver.org). Suggest adding "kubernetesVersion: x.x.x" to operator.yaml.

If the value is still needed and it's missing perhaps the default can be set to the current k8s version found on cluster?

[kensipe]

This was a duplicate of #1266
and was closed with #1296

[kensipe]

Importantly... I've tested it and a missing kubernetesVersion or a malformed version is captured at package verify and package create

[kensipe]

Changing from kubVer issue
to verify of operatorVersion and kudoVersion
operatorVersion is required