Add support for Bluetooth appearance property in QBluetoothDeviceInfo

In the Bluetooth standard document -> Core Specification -> Appearance Values, the Bluetooth device has the appearance property, but there is no support for it in QBluetoothDeviceInfo.

so i suggest add a few new ones:

1. enum AppearanceMajorCategory
2. enum AppearanceSubCategory
3. void setDeviceAppearance(quint16 appearance);
4. AppearanceMajorCategory majorAppearance() const;
5. AppearanceSubCategory subAppearance() const;