CLI improvements for Qt 5.14+

Qt 5.14 adds a "--help-all" option, so include it in the autocompletion.
Qt 5.14 also warns on multiple additions of the same option, which we
accidently did (KAboutData and we ourselves called it), so don't do
that.
Also fixes device autocompletion, which I accidently broke.

cli/kdeconnect-cli.cpp

@@ -83,7 +83,6 @@ int main(int argc, char** argv)
     parser.addOption(deviceAutocomplete);
     about.setupCommandLine(&parser);
 
-    parser.addHelpOption();
     parser.process(app);
     about.processCommandLine(&parser);
 
@@ -167,7 +166,7 @@ int main(int argc, char** argv)
         }
 
         //Exit with 1 if we didn't find a device
-        return int(!devices.isEmpty());
+        return int(devices.isEmpty());
     } else if(parser.isSet(QStringLiteral("refresh"))) {
         QDBusMessage msg = QDBusMessage::createMethodCall(QStringLiteral("org.kde.kdeconnect"), QStringLiteral("/modules/kdeconnect"), QStringLiteral("org.kde.kdeconnect.daemon"), QStringLiteral("forceOnNetworkChange"));
         blockOnReply(DBusHelper::sessionBus().asyncCall(msg));

cli/kdeconnect.zsh

@@ -17,6 +17,7 @@ _kdeconnect_device-ids() {
 local blockoperations="(operation sms)"
 _arguments -s \
   '(-)'{-h,--help}'[display usage information]' \
+  '(-)--help-all[display usage information, including Qt specific options]' \
   + '(global)' \
   $blockoperations{-l,--list-devices}'[list all devices]' \
   $blockoperations{-a,--list-available}'[list available (paired and reachable) devices]' \