Ability to define the role of a link without having to use the set button

[bgittel]

all my annotators complain about a small issue: I have a layer with a link feature. In order to annotate it, one has 1) to select the kind of link feature in the annotation or curation mode and 2) one has to click "Set". The second step is superfluous and leads to a lot of easy mistakes in practice (because if you forget it, you will annotate not the link feature but a new autonomous span)