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/ContainerSetSlotPacket.cpp

@@ -22,7 +22,7 @@ ContainerSetSlotPacket::ContainerSetSlotPacket(int containerId, int slot, shared
 {
 	this->containerId = containerId;
 	this->slot = slot;
-	this->item = item == NULL ? item : item->copy();
+	this->item = item == nullptr ? item : item->copy();
 }
 
 void ContainerSetSlotPacket::handle(PacketListener *listener)