Annotated Corpus Map: allow selecting Cluster ID as label

[wvdvegte]

Is your feature request related to a problem? Please describe.
If Annotated Corpus Map is set to produce a lot of clusters with Show cluster hull and/or Color points by cluster checked, it becomes hard to distinguish which color corresponds to which cluster (as was correctly pointed out by @janezd here).

Describe the solution you'd like
It would help if the cluster ID could also be selected as label, resulting in something like this:

Describe alternatives you've considered
An alternative would be to connect another Annotated Corpus Map to the output of the original one, which contains a column Cluster, so that it can be selected as label (in fact that's how I created the screenshot above). This solution doesn't look very elegant, though.