include magic method for setting local via Languages menu

I have found no explanation of what should work and why, but language
choosers seem to always include this line.  This also seems to fix the
bug:

closes #943

app/src/main/java/org/fdroid/fdroid/Languages.java

@@ -136,6 +136,7 @@ public final class Languages {
                 locale = new Locale(language);
             }
         }
+        Locale.setDefault(locale);
 
         final Resources resources = contextWrapper.getBaseContext().getResources();
         Configuration config = resources.getConfiguration();