Support @Named annotation

[ljacqu]

Support injections with @Named.

• How can @Named beans be registered manually to the injector?
• Do we want to pick up @Named on class declarations themselves? Means we'd need to extend the injector to be able to associate a bean to interfaces and its superclasses, which entails a potential big rework... (see also Add non-default handler that "autowires" interface #34)
• If the same bean is injected without @Named, it should be another instance
• Add a default name if no @Named annotation is provided?
• Allow to retrieve beans by name?
• What happens on name clash? On name clash of implicit types? (Potential breaking change)

[ljacqu]

Relates to #44