(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>
This also has a pretty generic name for a pretty specific task - since it is only for installing puppet-release repos.