Enable fallback to parsing POST data as a blob

If no 'json' key is found in POST data, fallback to parsing the entire POST body breaking messages on a delimiter. Both the fallback itself and the delimiter are configurable. This allows the ingestion of, for example, log messages that are simple strings delimited by newlines.

I have tested this in my environment and it appears to be working, though I have only tested with light load.

This may not be something you're interested in including in this plugin, or you may think I have gone about this the wrong way. All feedback is welcome.

Thanks for your consideration.