(NDK) Added explicit initialisation

Components and systems just can't be initialized at startup, so we need
some kind of explicit initialisation. I followed the same layout as the
others modules by adding a core class (Ndk::Sdk) which will initialize
components and systems, and Nazara's modules.

This is starting to get serious, I like it.


Former-commit-id: 263500e8d16db70ef7f92047b8a7e3235c08bcd0

SDK/include/NDK/BaseSystem.hpp

@@ -17,7 +17,8 @@ namespace Ndk
 
 	class NDK_API BaseSystem
 	{
-		friend class Entity;
+		friend class Sdk;
+		friend Entity;
 		friend World;
 
 		public:
@@ -55,6 +56,9 @@ namespace Ndk
 
 			void SetWorld(World& world);
 
+			static bool Initialize();
+			static void Uninitialize();
+
 			std::vector<EntityHandle> m_entities;
 			NzBitset<nzUInt64> m_entityBits;
 			NzBitset<> m_excludedComponents;