added: CLI opts & vers mins in create_cluster.sh
This adds a number of CLI switches to allow the common items to be changed from the defaults. In additon, it adds some sanity checking for the options before handing off to openshift-install.
The semver_compare has been added to enforce minimum software versions of dependent utiilities. The minimum versions for openshift-install and oc have been set to 4.6
Signed-off-by: Gerard Hickey ghickey@gitlab.com