writing to an Excel-file or CSV-file

[vvim]

See fc027f1 , line 1266 of buurtijd_deelnemers.cpp

Instead of using a QTextStream, maybe we can dive into one of the following libraries to create an Excel-file or CSV-file:

• QtCSV https://github.com/iamantony/qtcsv#1-quick-example
  • https://forum.qt.io/topic/16586/how-to-write-csv-file-in-qt/5
• http://qtxlsx.debao.me/
• http://www.qtsoftware.de/vertrieb/db/qtxls_e.htm
• http://stackoverflow.com/questions/16536933/qt-excel-editor
• https://wiki.qt.io/Handling_Microsoft_Excel_file_format