Check that zone value for a node is not null
Added functionality to get store schema

Example:
==========

 curl http://localhost:8080/schemata/dGVzdA==
{"key-serializer": "SerializerDefinition(name = string, schema-info =
{}, compression = null)", "value-serializer": "SerializerDefinition(name
= string, schema-info = {}, compression = null)"}
Cleaned up code based on Vinoth's review