BUG 2155 - depth parameter in NormalizedNodeWriter

For stable helium

- NormalizedNodeWriter - added depth class field (maxDepth, currentDepth)
  to make it possible to manage how deeply will be normalized node
  structure walked during generating output strea (JSON, XML).
  Presence of various normalized node will change current depth as
  follows:
  - ContainerNode = +1,
  - ListEntryNode (MapEntryNode, UnkeyedListEntryNode) = +1,
  - calling of endNode() method will decrease currentDepth by 1.

Change-Id: I7342581f4a1de25f8e8bb50ac0933258d7e3bce5
Signed-off-by: Jozef Gloncak <jgloncak@cisco.com>