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/JsonArray/size.cpp

@@ -6,8 +6,7 @@
 #include <catch.hpp>
 
 TEST_CASE("JsonArray::size()") {
-  DynamicJsonBuffer _jsonBuffer;
-  JsonArray& _array = _jsonBuffer.createArray();
+  DynamicJsonArray _array;
 
   SECTION("increases after add()") {
     _array.add("hello");