Added pulp::admin to install and configure pulp-admin tool

Makes it easier to add pulp-admin to the server or another admin machine.
In order to change the default settings, you'll need to add a parameter list here (something like https://github.com/pulp/pulp_packaging/blob/master/puppet/pulp/manifests/consumer.pp#L5). I recommend getting rid of the pulp::admin::params and using the values you set there as the defaults here.