Add support for app termination

[fgm]

Some services define a method to be called on termination, often a func (Foo) Close() error to implement io.Closer.

Currently, the container users need to know exactly which services need that, and call these functions in main.

It would be nicer to have the container support auto-closing, by allowing services to register some special termination optional interface the container could close in a single call to err := dic.Close(). The main issue is to ensure closure in in the inverse order of instantation to avoid breaking dependencies.