bluez5

- [x] Fix Adapter.create_paired_device (-> Adapter.create_device + Device.pair)

- [x] Check / Port usages of service interfaces in applet plugins (org.bluez.Network, org.bluez.Serial, org.bluez.AudioSink, org.bluez.AudioSource, org.bluez.Headset, org.bluez.Serial)

- [x] Check / Port direct signal handling (blueman/plugins/applet/PowerManager.py, blueman/plugins/applet/ShowConnected.py, blueman/plugins/applet/SerialManager.py, apps/blueman-applet (*))

- [x] Check / Replace all usages of get_interface outside of blueman.bluez

- [x] Fix on_device_property_changed https://github.com/blueman-project/blueman/pull/30#issuecomment-39030830

- [x] Discovery does not stop <del>(probably fixed by (*))</del>

- [x] Check agent API (Release, RequestPinCode, RequestPasskey, DisplayPasskey, RequestConfirmation, Authorize, ConfirmModeChange, Cancel)

- [x] Check / Port usages of main.Device#__getattr__ <del>(used for Services)</del>

- [x] Fix agent registration

- [x] Port Device.CancelDeviceCreation

- [x] Fix Device.list_services (https://github.com/blueman-project/blueman/pull/30#issuecomment-41013091)

- [x] Investigate why "Add device" appears in BlueZ 5 (https://github.com/blueman-project/blueman/pull/30#issuecomment-41012811)

- [x] <del>Fix / Port Device.Disconnect (does not exist in bluez 5, BUT only used in blueman/plugins/applet/DBusService.py:86 - usage seems to be wrong, refers to blueman.main.Device!)</del>

- [x] <del>Remove(?) ServiceInterface</del>

- [x] Pairing blocks GUI

- [x] Port Device.DiscoverServices

- [ ] Port audio device support (PulseAudioProfile)

- [ ] Port serial device support (Services["serial"] in applet plugins)

- [ ] Port services support in blueman-assistant

- [ ] Port services support in RecentConns

- [ ] Connection to generic services (HID and audio) does only seem to work right after discovering / pairing; throws "Input/output error" (mouse) or "No such file or directory" (smartphone; not connectable?)

- [ ] Custom passkey not working

- [ ] No pairing notifications depending on device?!

- [ ] Re-Enabling AuthAgent plugin tries to re-register GlobalAgent