Classifier Export: Trigger a "Save as" Dialogue

[jluethi]

Currently it's a text field where the user enters the full file path and it contains a reasonable default.
Better: When the user clicks the export button, trigger a "save as" dialogue, where the user can interactively select the destination and set the filename in the typical interface for a given operating system

[MaksHess]

Cool idea, this would also allow easy access to multiple versions of the same classifier :)

[jluethi]

It's not the prettiest implementation, but it works :)

If the user specifies a new save as path, the classifier is renamed and save in this new location.
Some funny edge cases still when it's not in the current working directory, as the classifier name currently is just the filename, not the full path. Will be doing a small refactor of that, then it should be ready

[jluethi]

Ok, fixed the saving now so it respects the directory a user is putting it in.

One limitation of the current implementation: If the user clicks "select file" and chooses a new file location, then confirms this in the pop up box, that does not save the file yet. This only confirms the new path. The user needs to click "Save Classifier".

I have not figured out a way to have the select file action actually trigger the saving, which may be confusing to the user, because the automatically generated file selection window says "save" as a confirmation...