Fixed createDataSetsFromRegion, labelRegion and categoryData.

* Fixed createDataSetsFromRegion

The way we where dealing with multi-dimensional cell regions, means cellRegion.width()>1 %% cellRegion.height()>1, was wrong. That could lead in us completly ignoring complete rows/columns.

1) proper sorted either from left-to-right if the dataDirection is Qt::Horizontal or from top-to-bottom when Qt::Vertical.
2) have multiple dimensions proper split-up into single rows/columns to produce one DataSet per row/column.

* Fixed labelRegion

1) Fallback to internalTable for labels.
2) Fix random index-number fetching caused by using depending on a proper value for dataSetNumber to calc the labelRowCol index offset.

* Fixed DataSet::categoryData to return the expected category-data for multi-dimensional cell regions.

* Use table:table-columns and table:table-header-columns to set the number of columns to a minimum rather then ignoring such definitions.

* Guard against multiple table-header-rows definitions in the XML that could end in us dealing with wrong header vs data offsets.