BUG-1442: integrate XML/JSON Normalized Node writers with Restconf

Integrated XML and JSON NormalizedNodeWriters for returning
data from Restconf. This writers does stream processing
and writes data into input stream without any intermediate
representations.

This will help with larger data sets, since it theoretically
reduces memory footprint of reading data from MD-SAL.

Change-Id: I36564b7a5a1bc50d60e1cb6d5b2b45f92c2caf0b
Signed-off-by: Jozef Gloncak <jgloncak@cisco.com>
Signed-off-by: Robert Varga <rovarga@cisco.com>
Merge "BUG-1442: integrate XML/JSON Normalized Node writers with Restconf"