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/TamableAnimal.h

@@ -33,6 +33,6 @@ public:
 	virtual void setSitting(bool value);
 	virtual wstring getOwnerUUID();
 	virtual void setOwnerUUID(const wstring &name);
-	virtual shared_ptr<Mob> getOwner();
+	virtual std::shared_ptr<Mob> getOwner();
 	virtual SitGoal *getSitGoal();
 };