Basic Perforce provider

Should look and feel like the other SVN/HG/etc... providers.  I had to add a few Perforce specific parameters and support for Workspaces.  I may need to enhance the use of Workspaces later, but this should get most Perforce users started.
Should these perhaps be `Puppet.debug` messages instead of `notice` messages? Also, if you're printing the config, the password would be printed in plaintext in the log.