forgot to replace this.bgColor by background in CVWidget
… working on the integration of CVWidgetMS in CVCenter

Signed-off-by: nuss <st9fan@gmail.com>
adapting CVCenter to work with CVWidgetMS:
several methods updated
small bugfix in CVWidget2D

Signed-off-by: nuss <st9fan@gmail.com>
fix closing editors when CVCenter gets closed

Signed-off-by: nuss <st9fan@gmail.com>