Enable provider injection

[mikey]

The IoC container should allow provider injection, meaning that something like

class FooProvider implements stubInjectionProvider
    /**
     * @Inject
     * @Provider('my::concrete::Bar')
     */
    public function setBar(stubInjectionProvider $barProvider) { ... }
}

should work. Just an idea at this points, this needs further thoughts but should be noted so it is not forgotten.

This depends on #189.

[mikey]

No usecase for now, maybe later.