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/copy.cpp

@@ -6,7 +6,6 @@
 #include <catch.hpp>
 
 TEST_CASE("JsonVariant copy") {
-  DynamicJsonBuffer _jsonBuffer;
   JsonVariant _variant1;
   JsonVariant _variant2;
 
@@ -43,7 +42,7 @@ TEST_CASE("JsonVariant copy") {
   }
 
   SECTION("ObjectsAreCopiedByReference") {
-    JsonObject &object = _jsonBuffer.createObject();
+    DynamicJsonObject object;
 
     _variant1 = object;
 
@@ -53,7 +52,7 @@ TEST_CASE("JsonVariant copy") {
   }
 
   SECTION("ArraysAreCopiedByReference") {
-    JsonArray &array = _jsonBuffer.createArray();
+    DynamicJsonArray array;
 
     _variant1 = array;