Fix untranslated strings and merge community translations

Bug fix

• Five strings no longer show in English on translated systems. "Language", "System Default", the desktop Mac charger banner, the USB device count in the status bar, and the "No e-marker detected" bullet were all missing from one or more translation files. Fixed across all shipped languages. Thanks to @bovirus for the detailed screenshots in the report.

Translation improvements

• Italian: improved wording for several strings, plus proper plural forms for device counts (from @bovirus).
• Armenian: 112 new Core translations (from @Vardan933).