Don't use JsonBuffer to create or parse objects and arrays.

* Added DynamicJsonArray and StaticJsonArray
* Added DynamicJsonObject and StaticJsonObject
* Added DynamicJsonVariant and StaticJsonVariant
* Added deserializeJson()
* Removed JsonBuffer::parseArray(), parseObject() and parse()
* Removed JsonBuffer::createArray() and createObject()

test/JsonVariant/set_get.cpp

@@ -122,9 +122,8 @@ TEST_CASE("JsonVariant set()/get()") {
 #endif
 
   SECTION("CanStoreObject") {
-    DynamicJsonBuffer jsonBuffer;
-    JsonObject &object = jsonBuffer.createObject();
+    DynamicJsonObject object;
 
-    checkReference(object);
+    checkReference<JsonObject>(object);
   }
 }