fix pivot fails in case of multi columns and multi data

[lbraconnier2]

PR Details

The pivot generation fails when pivot has many colums and many data.
Please se details below.

Description

i'll try to generate this pivot :

The database is this one :

Month	Year	Type	Sales	Region
Jun	2017	Produce	4059	West
Jul	2018	Meat	456	East
Mar	2018	Beverages	89	East
Mar	2017	Dairy	3237	North
Dec	2017	Meat	1258	South
Aug	2018	Meat	2790	South
Feb	2017	Produce	1831	West
Sep	2017	Produce	1485	North
Feb	2018	Beverages	563	West
Apr	2018	Meat	1159	West
Oct	2018	Dairy	2199	East
Feb	2019	Beverages	4703	South
Dec	2017	Dairy	156	North
Sep	2019	Beverages	4783	North
Aug	2017	Beverages	4718	South
Jul	2018	Produce	2996	East
Apr	2017	Dairy	3133	West
Aug	2019	Produce	3891	North
Mar	2018	Beverages	4107	East
Aug	2017	Produce	2205	North
Oct	2018	Produce	4757	South
Mar	2018	Dairy	3590	East
Jul	2018	Produce	3582	East
Feb	2019	Dairy	4271	North
Mar	2018	Dairy	2079	North
Jul	2019	Beverages	4819	West
Jan	2017	Dairy	710	South
Feb	2019	Beverages	4384	South
Jan	2019	Meat	1532	East
Dec	2019	Beverages	2051	East

The code for this pivot is :

if err := f.AddPivotTable(&PivotTableOption{
		DataRange:       "Sheet1!$A$1:$E$31",
		PivotTableRange: "Sheet2!$A$56:$AG$90",
		Rows:            []PivotTableField{{Data: "Month", DefaultSubtotal: true}, {Data: "Year"}},
		Columns:         []PivotTableField{{Data: "Region", DefaultSubtotal: true}, {Data: "Type"}},
		Data:            []PivotTableField{{Data: "Sales", Subtotal: "Sum", Name: "Sum of Sales"}, {Data: "Sales", Subtotal: "Average", Name: "Average of Sales"}},
		RowGrandTotals:  true,
		ColGrandTotals:  true,
		ShowDrill:       true,
		ShowRowHeaders:  true,
		ShowColHeaders:  true,
		ShowLastColumn:  true,
	}); err != nil {
		fmt.Println(err)
	}

but this won't generate proper pivot table and end up with pivot table removed in the generated excel.

After doing comparison of "\xl\pivotTables\pivotTable1.xml",
the one that is working(generated manually) got colFields generated like,

<colFields count="4">
		<field x="5"/>
		<field x="6"/>
		<field x="7"/>
		<field x="-2"/>		 
</colFields>

The one by exelize is :

<colFields count="3">
		<field x="5"/>
		<field x="6"/>
		<field x="7"/>	 
</colFields>

Related Issue

Motivation and Context

How Has This Been Tested

go test TestAddPivotTable

Types of changes

• Docs change / refactoring / dependency upgrade
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[codecov-commenter]

Codecov Report

Merging #710 into master will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #710   +/-   ##
=======================================
  Coverage   95.52%   95.53%           
=======================================
  Files          31       31           
  Lines        8386     8390    +4     
=======================================
+ Hits         8011     8015    +4     
  Misses        226      226           
  Partials      149      149           

Impacted Files	Coverage Δ
pivotTable.go	98.77% <100.00%> (+0.01%)	⬆️

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[xuri]

LGTM, thanks @lbraconnier2.