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/merge.go

@@ -0,0 +1,34 @@
+package qson
+
+// merge merges a with b if they are either both slices
+// or map[string]interface{} types. Otherwise it returns b.
+func merge(a interface{}, b interface{}) interface{} {
+	switch aT := a.(type) {
+	case map[string]interface{}:
+		return mergeMap(aT, b.(map[string]interface{}))
+	case []interface{}:
+		return mergeSlice(aT, b.([]interface{}))
+	default:
+		return b
+	}
+}
+
+// mergeMap merges a with b, attempting to merge any nested
+// values in nested maps but eventually overwriting anything
+// in a that can't be merged with whatever is in b.
+func mergeMap(a map[string]interface{}, b map[string]interface{}) map[string]interface{} {
+	for bK, bV := range b {
+		if _, ok := a[bK]; ok {
+			a[bK] = merge(a[bK], bV)
+		} else {
+			a[bK] = bV
+		}
+	}
+	return a
+}
+
+// mergeSlice merges a with b and returns the result.
+func mergeSlice(a []interface{}, b []interface{}) []interface{} {
+	a = append(a, b...)
+	return a
+}