Json deserialization support in java client

[kevinbheda]

Is your feature request related to a problem? Please describe.
We want to add support to deserialize json data based on the provided schema

Describe the solution you'd like
As of now the client only has protobuf deserialization support, need to create generic interface contract for Deserializer which will be implemented for various data formats. On the lines of

1. KafkaJsonSchemaDeserializer.java
2. KafkaAvroDeserializer.java
3. KafkaProtobufDeserializer.java
   We need to do some poc on return type, whether to return actual class object or generic json object. But regardless of it, it should validate whether the given input data is compatible with the schema or no.

Additional context
We need this because we want to support different input data types in firehose, which currently only supports protobuf.