Display transition condition instead of transition name in workflow graph

It is useless to display in the middle of a link between two nodes the transition name (which we already display at the root of the link actually). It is more interesting to see the condition, when it is different than "true".

Also, when adding a transition, studio should generate an id automatically, that the user can modify if he wants somehting more meaningful. Indeed, most of the time transitions name are not interesting.