[COOK-3691] Add LWRP

https://tickets.opscode.com/browse/COOK-3691

This is my implementation for COOK-3691.  The default behavior (include_recipe "openvpn") remains the same, but it now uses an LWRP to actually create the server config.  The user has the option to skip the default server config, but still get the openvpn installation, by setting node["openvpn"]["configure_default_server"] to false.  He or she can then create multiple tunnel/server configurations using the LWRP.  The provider supports more attributes than are used in the default recipe.