NiFi Processor - populate/consume native NiFi with full metadata integration

Our existing NiFi processors hand off XML to NiFi.

This ticket is for a more tightly integrated processor which takes a DFDL schema for data and hands off a NiFi data record, described by the DFDL schema, to NiFi so that its native access and manipulation of data can be applied.

This is different from handing off XML. In the XML case, NiFi can only manipulate or observe things about the XML by invoking XML libraries on it - e.g., extract an element to examine it using an XPath expression, etc.