Add a new option to Scroller (displayLabel)

[lvmajor]

Add a new initialization option for Scroller to let the user decide if he wants a label to be displayed when scrolling using the scrollbar (the black label floating left of the pointer). I mention "using the scrollbar" as the label update is (and was already) bound to the mousedown event so that doesn't change for now.

[lvmajor]

I don't know if that should be worth a patch version bump (or even minor)? As it adds a new option (without breaking change) I guess it should be a minor update, but I'm not 100% sure on what versioning strategy you're using, so I'll leave it up to you if you ever want to merge this :)

[DataTables]

Fantastic PR - thank you. Are you happy for this to be included under the MIT license?

Yes, this should really get a 2.x version number since its a new feature... I'll add that as I'm packaging it up for release.

[lvmajor]

@DataTables No problem with the MIT license here but I would have a small question for you regarding this.

Is there a way to agree once for all PR in any datatables repository? As I already did propose some other PRs in other repos and each and every time I get asked about the license (which is fine as I understand you must be sure the person knows the terms of the contributions). Maybe it could be good to have an "external contributors" list in which you could keep who accepted to commit their code and let you use it within the project's scope and related license?

As for the versioning, I'm not 100% sure this would require updating the major version as this does not cause any breaking change (so there's no reason for people updating their packages to "freak out" as they see a new major version)... but if you think it is worth updating the major version, then I have no problem with it :)