Currently, the file dialog tries to remember from where it is called and re-open in the last used directory. It also tries to be smart about the file type it shows by default. But because it wraps QFileDialog, there's always tension between the selected mimetype and the mimetypes used to filter the files shown. We need to figure out how the file dialog should _really_ behave on:
- file open
- file save as
- file export as
- select directory
coupled with the
- current file format of the active image
- the last used file format when saving as
- the last used file format when exporting
- the file types the user would like to see (the mimetype filter)
- the file type the user would like to use
- the last used location.