Project modernization (#630)

* Fixed boats falling and a TP glitch #266

* Replaced every C-style cast with C++ ones

* Replaced every C-style cast with C++ ones

* Fixed boats falling and a TP glitch #266

* Updated NULL to nullptr and fixing some type issues

* Modernized and fixed a few bugs

- Replaced most instances of `NULL` with `nullptr`.
- Replaced most `shared_ptr(new ...)` with `make_shared`.
- Removed the `nullptr` macro as it was interfering with the actual nullptr keyword in some instances.

* Fixing more conflicts

* Replace int loops with size_t and start work on overrides

Minecraft.Client/WitchRenderer.cpp

@@ -18,7 +18,7 @@ void WitchRenderer::render(shared_ptr<Entity> entity, double x, double y, double
 
 	shared_ptr<ItemInstance> item = mob->getCarriedItem();
 
-	witchModel->holdingItem = item != NULL;
+	witchModel->holdingItem = item != nullptr;
 	MobRenderer::render(mob, x, y, z, rot, a);
 }
 
@@ -38,7 +38,7 @@ void WitchRenderer::additionalRendering(shared_ptr<LivingEntity> entity, float a
 
 	shared_ptr<ItemInstance> item = mob->getCarriedItem();
 
-	if (item != NULL)
+	if (item != nullptr)
 	{
 		glPushMatrix();