Add Index field for BucketInfo

[ququzone]

Query

query{
  delegate(startEpoch: 10928, epochCount: 1, delegateName: "longz"){
    bucketInfo{
      exist
      bucketInfoList{
        epochNumber
        bucketInfo{
          isNative
          voterEthAddress
          votes
          remainingDuration
          decay
        }
        count
      }
    }
  }
}

Scheme:

Index field stored in buckets tables.

[newyear6565]

cannot be solved w/o rpc api support