shared_ptr -> std::shared_ptr

This is one of the first commits in a plan to remove all `using namespace std;` lines in the entire codebase as it is considered anti-pattern today.

Minecraft.World/KillCommand.cpp

@@ -9,9 +9,9 @@ EGameCommand KillCommand::getId()
 	return eGameCommand_Kill;
 }
 
-void KillCommand::execute(shared_ptr<CommandSender> source, byteArray commandData)
+void KillCommand::execute(std::shared_ptr<CommandSender> source, byteArray commandData)
 {
-	shared_ptr<Player> player = dynamic_pointer_cast<Player>(source);
+	std::shared_ptr<Player> player = dynamic_pointer_cast<Player>(source);
 
 	player->hurt(DamageSource::outOfWorld, 1000);