bundle qson lib in util (#1561)

* copy qson from https://github.com/joncalhoun/qson
  as author not want to maintain repo
* latest code contains our fix to proper decode strings
  with escaped & symbol
* replace package in api/handler/rpc

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

util/qson/README.md

@@ -0,0 +1,55 @@
+# qson
+
+This is copy from https://github.com/joncalhoun/qson
+As author says he is not acrivelly maintains the repo and not plan to do that.
+
+## Usage
+
+You can either turn a URL query param into a JSON byte array, or unmarshal that directly into a Go object.
+
+Transforming the URL query param into a JSON byte array:
+
+```go
+import "github.com/joncalhoun/qson"
+
+func main() {
+  b, err := qson.ToJSON("bar%5Bone%5D%5Btwo%5D=2&bar[one][red]=112")
+  if err != nil {
+    panic(err)
+  }
+  fmt.Println(string(b))
+  // Should output: {"bar":{"one":{"red":112,"two":2}}}
+}
+```
+
+Or unmarshalling directly into a Go object using JSON struct tags:
+
+```go
+import "github.com/joncalhoun/qson"
+
+type unmarshalT struct {
+	A string     `json:"a"`
+	B unmarshalB `json:"b"`
+}
+type unmarshalB struct {
+	C int `json:"c"`
+}
+
+func main() {
+  var out unmarshalT
+  query := "a=xyz&b[c]=456"
+  err := Unmarshal(&out, query)
+  if err != nil {
+  	t.Error(err)
+  }
+  // out should equal
+  //   unmarshalT{
+	// 	  A: "xyz",
+	// 	  B: unmarshalB{
+	// 	  	C: 456,
+	// 	  },
+	//   }
+}
+```
+
+To get a query string like in the two previous examples you can use the `RawQuery` field on the [net/url.URL](https://golang.org/pkg/net/url/#URL) type.