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/SwampTreeFeature.cpp

@@ -14,7 +14,7 @@ bool SwampTreeFeature::place(Level *level, Random *random, int x, int y, int z)
 	if (y < 1 || y + treeHeight + 1 > Level::genDepth) return false;
 
 	// 4J Stu Added to stop tree features generating areas previously place by game rule generation
-	if(app.getLevelGenerationOptions() != NULL)
+	if(app.getLevelGenerationOptions() != nullptr)
 	{
 		LevelGenerationOptions *levelGenOptions = app.getLevelGenerationOptions();
 		bool intersects = levelGenOptions->checkIntersects(x - 3, y - 1, z - 3, x + 3, y + treeHeight, z + 3);