Stacked Bar: Do not show label if only one bar is visible

[benib]

Todo

• create a temp view in CouchDB to get a list of all existing graphics that are stacked bars and have only one bar
• make a list with all the IDs that need to be adapted once the label will be hidden (by making sure the title/subtitle contains the information that is in the label)
• change the vega config mapping for stacked bars to make sure the label is not shown if there is a single bar