BasicViewerState removeSources has a typo which messes up SourceGroups

[NicoKiaru]

If a Source is present in a SourceGroup, calling state.removeSources will remove the sources from the viewer and the 'main' panel works, but it stays in the SourceGroup.

Also, when removeSources is called, all sources from all SourceGroup are removed (and it does not care about the argument of removeAll method).

I think this is due to a typo here:

bigdataviewer-core/src/main/java/bdv/viewer/BasicViewerState.java

Line 840 in 4d3550f

sourceToGroupAssignmentChanged |= groupData.sources.removeAll( sources );

It's rather:

sourceToGroupAssignmentChanged |= groupData.sources.removeAll( collection );

This would solve

bigdataviewer/bigdataviewer-playground#272

and maybe ?
#146

I'll make a quick PR

[NicoKiaru]

Here's the PR: #178

I think I did a small mistake in the PR since there's an extra commit from Tobias. I don't know ow it came in the PR

[NicoKiaru]

PR #178 merged, so let's close this issue.