Updated the dependencies and scripts for python3:
* `python-dbus` no longer exists in Debian 11 'bullseye' or Ubuntu > 20.04, installl the `python3` version
* `python-gobject` has been superseeded by `python(3)-gi`, the current package is just a transitional package that pulls
`python-gi` and the old `python-gobject-2` (deprecated). Update the dependencies and the scripts to use the new package.
* set python3 as interpreter for the helper scripts. Fixed the dict syntax for getting items
* include some test scripts from the bluez5 repository as they are not readily available on jessie - meaning we don't have to rewrite everything
* use bluetoothctl for discovery of devices as hcitool scan lists devices, but doesn't make them available via bluez dbus api
