QtIFW

Unify translated error messages

* Enclose file paths in ""
* Localize file paths with QDir::toNativeSeparators.
* Make sure sentences end with a '.'
* Append error details always by ':', e.g.
    tr("Failed to copy file '%1': %2").(...)
* Use 'directory' instead of 'folder' everywhere

Change-Id: Ie045f429f72ad5045c96537465c5fb9d2e99d250
Reviewed-by: Karsten Heimrich <karsten.heimrich@theqtcompany.com>