Support for forChild

[soundlake]

In Angular2 Doc, it's suggested to use forRoot and forChild convention.

forRoot and forChild are conventional names for methods that deliver different import values to root and feature modules. Angular doesn't recognize them but Angular developers do.

Maybe it's only a convention, but it would be useful for big project with bunch of sub modules.

[lacolaco]

Thank you for your idea. I'll think about it.