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.Client/LavaSlimeModel.cpp

@@ -22,7 +22,7 @@ LavaSlimeModel::LavaSlimeModel()
             v = 19;
         }
         bodyCubes[i] = new ModelPart(this, u, v);
-        bodyCubes[i]->addBox(-4.0f, 16.0f + (float)i, -4.0f, 8, 1, 8);
+        bodyCubes[i]->addBox(-4.0f, 16.0f + static_cast<float>(i), -4.0f, 8, 1, 8);
     }
 
     insideCube = new ModelPart(this, 0, 16);