Enabled generic Entity.AddComponent<T>

Fixed: All the AddComponent<T>(IComponent component) method chain was
dead code by default:
entity.AddComponent(new MyComponent());
always chose non-generic Entity.AddComponent(IComponent component)
IComponent<T> interface is obsolete

Use entity.AddComponent(derived as BaseComponent) if you wish to use
derived component as a base component
Made use of generic EntityManager.AddComponent<T> in Entity.AddComponentFromPool<T>
Merge pull request #54 from Maximusya/enable-generic-addcomponent

Enable generic addcomponent