Extent existing Grid widget or add new Widget which allows to display an additional 'Total' column (Horizontal aggregation) or 'Total' row (vertical aggregation)
Horizontal in the case of an Aggregation of multiple measures (e.g KPI1 + KPI2 + KP3)
Vertical in the case of an Aggregation of 1 measure split by various dimensions (e.g Berlin-KP1 + Frankfur-KPI1, etct
Aggregation could be SUM, MINUS, AVERAGE
