Make the dr Mingw page more legible
List of changes introduced by this commit:
- It removes all the mentions of 3.0 beta version since we don't want any backtrace before 3.0 anyway, so all relevant versions should have dr Mingw already included.
- It changes the order of the content on the page to be more consistent to what people need - they first need to download a debug package and only then get a crash log. That way is, I believe, less confusing.
- It adds mentions of getting a portable version of Krita instead of trying to put debug symbols in the installed version.