Added jar_timeout parameter for when using http,https,ftp jarfile source...

Hello,

  Here is a pull request to add an optional jar_timeout parameter for when using a http https or ftp jarfile source.  The logstash jar is 78M which sometimes exceeds the default 5 min puppet exec timeout for me.  Having an extra parameter for timeout would allow users to be able to ensure a longer wait time.

Thanks,

- Tyler