OpenReach have kindly updated the firmware on the HG612.
The current sync speed text has changed to 'Bearer', so we look
for that now, as well as 'Path'.
Set the default to /var/lib/munin/plugin-state/huawei-hg612-munin-output.txt
for safety.
Include a crontab file to be placed in /etc/cron.d.
Update readme to match, and simplify.
