11. GetLocalChain 获取超块指定子链数据

* 参数: hid 超块号

chain_num 子链号

* 例子: http://127.0.0.1:8080/GetLocalChain?hid=1416&chain_num=1

* 返回例子：

{
  "block_chain":"unknown",
  "blocks":2,
  "chain_num":1,
  "concensus":"buddy",
  "difficulty":2
}