Modernize project codebase (#906)

* 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

* Add safety checks and fix a issue with vector going OOR

Minecraft.Client/ReceivingLevelScreen.cpp

@@ -23,9 +23,9 @@ void ReceivingLevelScreen::tick()
     tickCount++;
     if (tickCount % 20 == 0)
 	{
-        connection->send( shared_ptr<KeepAlivePacket>( new KeepAlivePacket() ) );
+        connection->send(std::make_shared<KeepAlivePacket>());
     }
-    if (connection != NULL)
+    if (connection != nullptr)
 	{
         connection->tick();
     }