User-configurable parameters available via config files

User-configurable parameters available via config files

User-configurable parameters available via config.yaml files - with all
defaults shown. Exact parameters and formats for these configuration
files are outside the scope of this requirement (and TBD by Genesis
team). The requirement is simply to be able to support parsing these
yaml config files as inputs to all installers.

JIRA: GENESIS-17

Change-Id: Id484d59205ce6b423329cfa0a86b7d6d22c04dba
Signed-off-by: Tim Rozet <trozet@redhat.com>