fix column position and colspan

1) Fix `colspan` value in grouping header from `colspans` to `(grp.groupColumnShow[n.idx] === false ? colspans-1 : colspans)`.
2) fix parameters of `buildSummaryTd` in case of `groupSummaryPos: ["header"]` and `groupColumnShow: [false]`. The current implementation places the summary in the old position