4. GetHyperBlockHead 获取超块头信息

* 参数: key块号

* 例子: http://127.0.0.1:8080/GetHyperBlockHead?key=10

* 返回例子：

{
  "br_root":"0101010101010101010101010101010101010101010101010101010101010101",
  "br_rule":0,
  "childchain_blockscount":[2],
  "ctime":1561702500,
  "hash":"a4f27b3cb570da42b7ad60b17980010e3bab9ce9bf7716a440b55bcf9e04ea6e",
  "hash_prev":"b57e9bf37663e5a8c2c88bf48090b96774384e5c0a206efe3aecfb35765789b1",
  "hash_prev_header":"2d761092128a891de17a98d3035bb7d773440473117ee59a3464fcc98795619d",
  "hid":10,
  "hyperBlockSize":114,
  "merkle_hash_all":"b3319e25bbb284017286ea5127a5a2f0b0b6e0892d6d3690560d7dee0511df0d",
  "script_hash":"0101010101010101010101010101010101010101010101010101010101010101",
  "tailblockshash":[
     "d345f8d3579e4f7410bec4494821077f489fcab4f198f3e2de48132e276a2605"
  ],
 
  "version":"1.0.0",
  "weight":2,
  "xw_hash":"0101010101010101010101010101010101010101010101010101010101010101"
}