module-jackdbus-detect: Add channel_map argument for sink

This is a fix for issue issue 249. I added a channel_map argument to module-jackdbus-detect, but it only forwards the channel map to module-jack-sink. Should I name the argument sink_channel_map instead to make it clear which module it will forward to? If so, should I add a source_channel_map as well? The original issue doesn't ask for that, but it wouldn't be hard to do. For that matter, do you think any of the other arguments to module-jack-sink or module-jack-source are work making proxies for (sink_properties, server_name, client_name)?