openshift.ks: Validate settings

set_defaults: Check for unrecognized or empty settings and abort if one is
found and verify that the list of components to install includes only valid
components.

This commit fixes bug 1097910.
<openshift.ks> Fix rhscl yum repo priority
Merge pull request #348 from detiber/rhscl-1.1(2.1)

Rhscl 1.1(2.1)
Merge pull request #340 from Miciah/enterprise-2.1/openshift.ks-validate-settings

openshift.ks: Validate settings  
Bug 1097910 has been verified
install: introduce VM image kickstart