Suppress empty columns in Kanban displaymode

[FaceCrap]

• intrudced new labels_used list
• moved tab_games_ids to higher up as we need those id`s to determine used labels and game counts.
• added a loop to get both labels and game counts per label used in current tab
• changed references from Label.instances to labels_used
• removed a second loop determining game count per label, already done higher up