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/Mob.h

@@ -27,7 +27,7 @@ class Mob : public LivingEntity
 public:
 	// 4J-PB - added to replace (e instanceof Type), avoiding dynamic casts
 	eINSTANCEOF GetType()						{ return eTYPE_MOB;}
-	static Entity *create(Level *level) { return NULL; }
+	static Entity *create(Level *level) { return nullptr; }
 
 public:
 	static const float MAX_WEARING_ARMOR_CHANCE;