Lay down master config files on the minion

Addresses issue #204, by giving salt-cloud (and aws as our guinea pig) the ability to lay down master config files.

In order to enable this, a user would set the following option in the profile/map:

    make_master: True

If this is set, then master.pub and master.pem will be generated. In order to also generate master config, a master section (similar to the minion section) must be set. For instance:

    master:
        user: root
        interface: 0.0.0.0

If no master section is specified, then no master config will be laid down. Since the master config rarely needs to be modified, this is appropriate for distributions whose install package already lays down a master config file (this is not always the case).

This does not completely resolve issue #204, since salt-bootstrap must also be able to handle the master configs.