Describe the bug

• When trying to Download a DataTable as CSV with special characters such as accents ('é', 'ô' etc.) it is not downloaded with the correct encoding so Excel reads the characters strangely
• Since this is an issue in htdocs, projects cannot modify it so we need this change in Core instead.
• The type of the Blob must be changed to text/csv;charset=utf-8; from text/csv
• the content parameter in the Blob constructer must have \uFEFF appended to the start

To Reproduce

• Insert a value in the datadict with an accent, or a user with an accent in their Full Name in User Accounts
• Press Download Table as CSV and open in Excel
• See strange characters instead of the accent

An example from the change on CCNA