Remove bzip2 compression support

Remove bzip2 compression support

It didn't work for exports bigger than 1 MB.
An alternative would be to remove the limit from output buffer which would need memory for the whole export.
Another alternative would be to create a temporary file in output handler and bzwrite() to this file - that would work but it's complicated, especially if we want to output the file progressively - bzopen($tmp, 'w'), fopen($tmp, 'r').