Setter function to set raw values into a cell

SetCellStr escapes the value in a cell so the excel sheet cannot use the value in formulas.

SetCellDefault accepts a string value and sets it to a cell as a raw value without escaping it

- New functions `GetActiveSheetIndex`, `GetSheetName` and `GetSheetMap` added.

- Update workbook and sheet relationships and self-close tag replacement hack functions

- Compatibility improved: relationship namespace in `workbook.xml` has been changed (`xmlns:mc`, `xmlns:x15` and `mc:Ignorable` added)

- Fix `GetCellValue` causes panic in some particular situation issues;
- Go test updated

- Fix issue XML tag `headerFooter` and `sheetPr` element self-close errors cause file corruption;
- Fix issue `Section` and `Pane` element order make file corruption in some case;
- Change sheet `rId` calculation method in `/xl/workbook.xml`, fix makes file corruption in some case;
- Compatibility improved: add `xlsxTabColor` struct and some XML element for worksheet

- Update import PKG syntax in struct;
- Update test XLSX file (include table, charts, functions, comments and hyperlink on Sheet1)

- Update test template for this fix

Fix hyperlink missing after save issue and update completion row element logic to enhance compatibility.

looping on rows columns functionality

Update README.md @schigh 👌 Thanks for your pr.

added missing imports

Revert "Update README.md"

Update README.md @schigh Thanks for u pull request.

Adding more realistic error handling in examples

Make readme highlight code

Open file error return added and UpdateLinkedValue function added to fix linked values within a spreadsheet are not updating.