Bug 189363 The aggregation of table should be start with sigma symbol
Description: Follow the spec, after specify a aggregation on a table, the aggregation should be represented by starting with the sigma symbol
xtab/org.eclipse.birt.report.item.crosstab.ui/src/org/eclipse/birt/report/item/crosstab/internal/ui/editors/action/AddSubTotalAction.java
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