<install> don't always set the hostname

If the "hostname" specified is an IP, don't set that.
Also, if they don't want their hostname overwritten, there's an option
for that.
Also, superseding the hostname in the dhcp conf appeared to do nothing
(or be overwritten by sysconfig) so it's removed.
Add additional named host entries when using named component

* Provide a NAMED_ENTRIES argument to the script or export
  CONF_NAMED_ENTRIES environment variable with comma delimited
  host:ipaddress pairs (colon delimited host and ipaddress)
openshift.ks: Delete NAMED_ENTRIES

configure_named: Instead of setting NAMED_ENTRIES=${CONF_NAMED_ENTRIES}
and then using NAMED_ENTRIES, just use CONF_NAMED_ENTRIES directly.
<install> ability to not create host DNS entries
<install> separate host DNS out from app
<install> ability to skip jboss repos/carts

Conflicts:
	enterprise/install-scripts/amazon/openshift-amz.sh
	enterprise/install-scripts/generic/openshift.sh
	enterprise/install-scripts/openshift.ks
<install> register to RHN with --force; re-runnable
<install> introduce yum CDN base URL; refactor accordingly
Merge pull request #92 from sosiouxme/enterprise-1.2-DNS

Enterprise 1.2 dns and other install script enhancements
<install> bind_key; preflight checks; docs

* added some preflight sanity checks like "is this RHEL 6?"
* compressed some verbose code defining yum repos
* after some research, discovered that the bind key is not half of a
keypair and can be set arbitrarily; re-enabled that ability.