Consider reporting "scanning" before "syncing" in main dialog

### Feature description
I've realised that the settings window has more detailed sync information than the main dialog, especially when performing the initial scan for file changes. When scanning large directories the main dialog appears frozen simply saying "Syncing file 0 of n", whilst the settings window informs you that it is scanning and you can see what folders are taking such a long time to scan.

It would be useful if this were better reported on the main dialog instead. Perhaps it should report that it is scanning rather than "syncing" until it actually starts syncing the files?

I assume you don't want the UI on the main dialog to be flicking through every directory that is being scanned like it does in the Settings window, but maybe something like:

> Scanning for changes, found n