Provide simple utility to enable OpenHPC repo from downloaded release tarball

[koomie]

Per TSC discussion, include a utility that an admin can run after downloading a copy of a release tarball containing a self-contained package repo.

[koomie]

This is live and is included with the pre-assembled distribution tarballs that are housed at:

http://build.openhpc.community/dist

After download, an administrator can run the utility to create a local copy of the repositories using repo data included in the tarball:

# ./make_repo.sh 
--> Creating OpenHPC.local.repo file in /etc/yum.repos.d
--> Local repodata stored in /root/repo