Improve end-user obserability

[bkeepers]

There is currently very little end-user feedback if the plugin is working. There are a lot of app.debug statements, but those don't show up by default unless debugging is enabled for the plugin.

Some of them could probably be switched to console.log or app.setPluginStatus

[bergie]

signalk-postgsail is a good example here, saying things like No data in queue, last connection to server was 3s ago in plugin status.