Use Label interface from saalfeldlab/label-utilities

[hanslovsky]

We currently have two Label interfaces, one in here and one in saalfeldlab/label-uiltities. We should use the one from saalfeldlab/label-utilities.

[igorpisarev]

What about doing this the other way around: keep the Label class in this repository and make label-utilities depend on this package? This way we would keep the basic label mutliset functionality in this repository with minimal dependencies.

[hanslovsky]

My reservation against that is that the Label class is not really related to label multisets. Maybe an imglib2-labels package would be the right place?