OpenBSD support

The main part of this patch is getting the module to support managing asterisk on OpenBSD.
Tested on OpenBSD 5.6-current, with asterisk-11.14.1, and puppet-3.7.3.

While there, and because I run the future parser, there are some enhancements making the module work with the future parser. Additionally to that, a few minor changes, which puppet-lint told me about.

The most "drastic" change is in manifests/service.pp, in the service, I removed the fairly unportable, start, stop and restart parameters. The service type should be clever enough to figure that out on its own, at least it does so on OpenBSD ;)

Other changes is the introduction of general parameters: asteriskuser, asteriskgroup, which contain the username/groupname of the account running asterisk. Then the astbinary, which points to the 'asterisk' binary location. Further, the group 'root' in config.pp was changed to just the userid: 0.
On OpenBSD, and other *BSD, there is no group root', but group wheel, with gid 0.

please review and apply, or comment, so I can fix or rework as you like.

Sebastian