IAM-XLS: Generate Excel spreadsheets in XLS format

This class can be used to generate Excel spreadsheets in XLS format.

It can add text or numeric values to given rows and columns of a spreadsheet.

The class may also execute a MySQL database query and generate a single spreadsheet with the results of the query. The first row has the query result column names.

The class stores the whole spreadsheet definition in XLS format in a class variable.

The generated spreadsheet data can be served for download. The class detects the browser type and issues the specific headers to make the browser handle the spreadsheet data file properly.