Add RegisterTo<TService, TTarget> method

Short hand for:
```c#
Register<TService, TTarget>(factory => factory.GetInstance<TTarget>())
```

This is useful for registering a group of interfaces that actually resolve to the same instance registered with a specific lifetime.

The following:
```c#
var container = new ServiceContainer();
container.Register<Concrete>(new PerRequestLifeTime());
container.Register<IInterfaceOne, Concrete>(factory => factory.GetInstance<Concrete>());
container.Register<IInterfaceTwo, Concrete>(factory => factory.GetInstance<Concrete>());
```

can now be written in:
```c#
var container = new ServiceContainer();
container.Register<Concrete>(new PerRequestLifeTime());
container.RegisterTo<IInterfaceOne, Concrete>();
container.RegisterTo<IInterfaceTwo, Concrete>();
```