Add blinkding

[donald]

blinkd.py script by @niclas and udev rule and sytemd service to run it, when the Blink LED is plugged in.

Currently this can't be used, because every invocation of blink1-tool generates BIND and UNBIND events, which brings upowerd to fill the log:

root@theinternet:~# journalctl -f
-- Logs begin at Tue 2018-03-27 12:08:10 CEST. --
Jul 03 16:19:54 theinternet.molgen.mpg.de upowerd[761]: unhandled action 'bind' on /sys/devices/pci0000:00/0000:00:14.0/usb3/3-8/3-8:1.0
Jul 03 16:19:54 theinternet.molgen.mpg.de upowerd[761]: unhandled action 'unbind' on /sys/devices/pci0000:00/0000:00:14.0/usb3/3-8/3-8:1.0
Jul 03 16:19:55 theinternet.molgen.mpg.de upowerd[761]: unhandled action 'bind' on /sys/devices/pci0000:00/0000:00:14.0/usb3/3-8/3-8:1.0
Jul 03 16:19:55 theinternet.molgen.mpg.de upowerd[761]: unhandled action 'unbind' on /sys/devices/pci0000:00/0000:00:14.0/usb3/3-8/3-8:1.0
Jul 03 16:19:55 theinternet.molgen.mpg.de upowerd[761]: unhandled action 'bind' on /sys/devices/pci0000:00/0000:00:14.0/usb3/3-8/3-8:1.0
Jul 03 16:19:55 theinternet.molgen.mpg.de upowerd[761]: unhandled action 'unbind' on /sys/devices/pci0000:00/0000:00:14.0/usb3/3-8/3-8:1.0
Jul 03 16:19:55 theinternet.molgen.mpg.de upowerd[761]: unhandled action 'bind' on /sys/devices/pci0000:00/0000:00:14.0/usb3/3-8/3-8:1.0
Jul 03 16:19:55 theinternet.molgen.mpg.de upowerd[761]: unhandled action 'unbind' on /sys/devices/pci0000:00/0000:00:14.0/usb3/3-8/3-8:1.0
Jul 03 16:19:55 theinternet.molgen.mpg.de systemd[1]: Stopping blinkd...
Jul 03 16:19:55 theinternet.molgen.mpg.de systemd[1]: Stopped blinkd.
^C

[donald]

Waitng for @niclas for new version which uses a to-be-installed python3 library. upowerd issue is resolved.