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.World/TextureAndGeometryChangePacket.cpp

@@ -49,5 +49,5 @@ void TextureAndGeometryChangePacket::handle(PacketListener *listener)
 
 int TextureAndGeometryChangePacket::getEstimatedSize() 
 {
-	return 8 + (int)path.size();
+	return 8 + static_cast<int>(path.size());
 }