FileBrowserComponent::deselect

As the title says, I think this method is missing, so it’s not easy to actually deselect the current selected item (need to enumerate child component and call deselectAllRows()).
It depends on the file display mode, but both sub-component have method for this.

It’s useful in case you’re not using a modal filebrowsercomponent.

Ok, sounds like a good idea, I’ll add something to do that.