Geomap: adding option to merge legend label and symbol

[Garneauma]

Geomap: Adding the option to hide the symbol's description when there is only one item in the legend layer as the description is most likely the same as the label.

Changes related to WET-450

[Garneauma]

Pre-approved upon successful review.

[duboisp]

Just a little change to add a comment for some clarity in the code.

I reviewed all the code/example and tested locally, everything do work as expected and nothing to report.

Once the little comment is added, it will be good to merge.

[duboisp]

Reviewed and all good.

This is a minor change.