Optimize AsciiFilter
Right now we need ca. 90s to import 2.9GB of data (5Mil rows and 6 columns). The profile for 1M rows is attached (callgrind.out.zip.
We spent quite some time in QLocale::toDouble() and in QString::split().
We switched to QLocale to properly deal with the locale specific decimal separators. We should maybe use QLocale to initially determine the format and then rely on std classes only when reading the data.
Similar for QString::split(), we should check some other techniques like maybe those mentioned in https://adamdrake.com/faster-command-line-tools-with-go.html#v4-stop-using-strings. If we manage to avoid using QString::split() we can get rid of constructing and destructing QStringList in every iteration in the for-loop which also takes a lot of time - doing this for a more faster container (c array?) will be faster.