Use Folder rather than Directory wording

[JohnVeness]

Relevant components

• [x] Standalone tray application (based on Qt Widgets)
• [x] Plasmoid/applet for Plasma desktop
• [x] Dolphin integration
• [ ] Command line tool (syncthingctl)
• [ ] Integrated Syncthing instance (libsyncthing)
• [x] Backend libraries

Is your feature request related to a problem? Please describe. Throughout the UI, the words directory & directories are used, when instead Syncthing uses the words folder & folders. Although the meaning is probably clear to most, it would be better to match Syncthing terminology.

Describe the solution you'd like Directory replaced with Folder etc.

Additional context I'm happy to submit a PR if you agree with this :)

[Martchus]

I know. I have never dared to take the effort to change it. It would likely make sense to change also all internal class/function names and descriptions and one had to take care that translations still work (without having to retranslate every affected string).

[JohnVeness]

Ah this is bigger than I thought - I didn't consider having to change internal names too, or translations! Another complication is that this isn't a simple search and replace - for example, the official Syncthing GUI refers to "directories" when showing the global or local size of a folder, and you also have a setting for a Qt plugin directory which probably shouldn't change.

[Martchus]

I suppose changing just the user-visible strings (and their translations) would nevertheless be the first step. Maybe I can find the time to look into that next week.

[JohnVeness]

I've had a go at this myself, if you're interested. See #206

[Martchus]

I've merged your PR and also added a few further commits for cleanup and completeness. This should cover all English and German user-facing strings.

[JohnVeness]

Many thanks :)

[Martchus]

I guess this can be considered done; not sure whether it makes sense to change the names of all internal functions/classes/files.