Add GSON to GiantCore

src/com/google/gson/DefaultDateTypeAdapter.java

src/com/google/gson/ExclusionStrategy.java

src/com/google/gson/FieldAttributes.java

src/com/google/gson/FieldNamingPolicy.java

src/com/google/gson/FieldNamingStrategy.java

src/com/google/gson/Gson.java

src/com/google/gson/GsonBuilder.java

src/com/google/gson/InstanceCreator.java

src/com/google/gson/JsonArray.java

src/com/google/gson/JsonDeserializationContext.java

src/com/google/gson/JsonDeserializer.java

src/com/google/gson/JsonElement.java

src/com/google/gson/JsonIOException.java

src/com/google/gson/JsonNull.java

src/com/google/gson/JsonObject.java

src/com/google/gson/JsonParseException.java

src/com/google/gson/JsonParser.java

src/com/google/gson/JsonPrimitive.java

src/com/google/gson/JsonSerializationContext.java

src/com/google/gson/JsonSerializer.java