Add support for setting the classic layout for pivot table

[Zncl2222]

Description

It seems that excelize does not support setting the classic layout for pivot tables currently.

Howevere I needed this function, so I made some adjustments to implement it.

You can find implementation here:

Zncl2222@5f7a4ce

The classic layout need to set Compact and CompactData to false, set GridDropZones to true in PivotTableDefinition, and set Outline and Compact in each field to false

I am happy to submit a PR if you find this idea valuable. If you approve this proposal, I will modify the commit message to follow the style of excelize's commit messages and add more test cases if needed.

Example

In this implementation Zncl2222@5f7a4ce, user only need to set the ClassicLayout to true in PivotTableOptions to configure the pivot table in classic layout.

The code snippet to create the pivot table with classic layout

package main

import (
	"fmt"

	"github.com/xuri/excelize/v2"

	"golang.org/x/exp/rand"
)

func main() {
	f := excelize.NewFile()
	defer func() {
		if err := f.Close(); err != nil {
			fmt.Println(err)
		}
	}()
	month := []string{"Jan", "Feb", "Mar", "Apr", "May",
		"Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"}
	year := []int{2017, 2018, 2019}
	types := []string{"Meat", "Dairy", "Beverages", "Produce"}
	region := []string{"East", "West", "North", "South"}
	f.SetSheetRow("Sheet1", "A1", &[]string{"Month", "Year", "Type", "Sales", "Region"})
	for row := 2; row < 32; row++ {
		f.SetCellValue("Sheet1", fmt.Sprintf("A%d", row), month[rand.Intn(12)])
		f.SetCellValue("Sheet1", fmt.Sprintf("B%d", row), year[rand.Intn(3)])
		f.SetCellValue("Sheet1", fmt.Sprintf("C%d", row), types[rand.Intn(4)])
		f.SetCellValue("Sheet1", fmt.Sprintf("D%d", row), rand.Intn(5000))
		f.SetCellValue("Sheet1", fmt.Sprintf("E%d", row), region[rand.Intn(4)])
	}

	if err := f.AddPivotTable(&excelize.PivotTableOptions{
		DataRange:       "Sheet1!A1:E31",
		PivotTableRange: "Sheet1!G2:M34",
		Rows: []excelize.PivotTableField{
			{Data: "Month", Name: "I Am Month", DefaultSubtotal: true}, {Data: "Year", Name: "I Am Year"}},
		Filter: []excelize.PivotTableField{
			{Data: "Region"}},
		Columns: []excelize.PivotTableField{
			{Data: "Type", DefaultSubtotal: true, Name: "I Am Columns"}},
		Data: []excelize.PivotTableField{
			{Data: "Sales", Name: "Summarize", Subtotal: "Sum"}},
		RowGrandTotals: true,
		ColGrandTotals: true,
		ShowDrill:      true,
		ShowRowHeaders: true,
		ShowColHeaders: true,
		ShowLastColumn: true,
		ClassicLayout:  true,
	}); err != nil {
		fmt.Println(err)
		return
	}

	if err := f.SaveAs("PivotTable.xlsx"); err != nil {
		fmt.Println(err)
	}
}

If the ClassicLayout property is unset or set to false, the pivot table will look like this: