Removed dependence on INITIAL_PARTITION_COUNT from MALHAR

   * Removed dependence on INITIAL_PARTITION_COUNT from MALHAR.
   * Added StatelessPartitioner to be used by operators which want a default partitoner which creates multiple partitions.
Can we change it to initialPartitionCount or add a comment saying "It is only used for initial partition count and it only takes effect when strategy is set to ONE_TO_MANY"