Add result lookup api

[zfarrell]

Enhance the query api to include a result identifier which can be used to retrieve the original query and result:

Submit query

POST /query
{
 "sql": "select * from Users limit 1"
}

Query result

200 OK

{
  "result_id": "abc-123",     --- the new "result id"
  "columns": [
    "id",
    "name"
  ],
  "rows": [
    [ 1, "John Smith"]
  ],
  "row_count": 1,
  "execution_time_ms": 1
}

Retrieve result

GET /query/result/abc-123
{
   "sql": "select * from Users limit 1"
   "result": {
      "result_id": "abc-123", 
        "columns": [
          "id",
          "name"
        ],
        "rows": [
          [ 1, "John Smith"]
        ],
        "row_count": 1,
        "execution_time_ms": 1
      }
}