Add jenkins_v1alpha2_jenkinsimage_crd.yaml

After upgrading to jenkins-operator:v0.5.0 the operator enters
crashloop backoff becasuse JenkinsImage CRD is missing. Adding this file
fixes the problem as per (disregard Helm mentionings):
https://github.com/jenkinsci/kubernetes-operator/issues/503

Change-Id: If4edd89d90bf2c7f438b98eb4f0073d1ff065733