(QENG-715) Add `install_dev_repo` to Beaker DSL

This is a "push" style method of installing a dev repo from
builds.puppetlabs.lan by first downloading to a directory on the local machine
then pushing to the appropriate configuration directory on the remote machine.

Signed-off-by: Wayne <wayne@puppetlabs.com>
@anodelman I think it needs to be an exact match, if you look at line 507 above the split is being done with the `-` as the separator which means the `variant` here will only contain `el` for that platform. Would `/^(fedora|el|centos)$/` be okay with you? If so I'll go ahead and make that change.