(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 Yeah, I pulled it out of classifier helper.rb and they pulled it out of puppet.

If we want to make this usable in puppet, should we update the yard docs so it's officially part of the DSL?