Added Json to CompositeNode translation

Added Json to CompositeNode translation

- added JsonReader.java to provide translation from Json (InputStream) to CompositeNode
- Json has to be in one of these two formats:
  {"foo":{....}} for Container foo
  {"foo":[{....}]} for List foo
- added preconditions to translation from Node to Json:
  Data of Container and List has to be represented as CompositeNode
  Data of LeafList and Leaf has to be represented as SimpleNode
- request for unexisting data has response - not found 404

Change-Id: I9f2a07a0d333b09803606e0e4275bdf39d2cdce5
Signed-off-by: Martin Sunal <msunal@cisco.com>