Rhubarbe

* rhubarbe-pdu reports power consumption in watts for outlets that are ON

* the pdu script uses SNMP to retrieve status (i.e. probe and status)
* bugfix: temporary files in /tmp/pdu*.txt were not properly cleaned up

* ci bugfix: the off command was not working when a soft reset was attempted
https://github.com/fit-r2lab/rhubarbe/issues/17

* PDUs become first-class citizens like nodes and phones
* `rhubarbe-pdu` replaces `rhubarbe-script` with subcommands
* `list` for seeing the static inventory (pdu_hosts and devices)
* `status` to inspect the status of a device or pdu_host
* `on`, `off` and `reset` that target an individual device
* `rhubarbe-monitorpdus` and related systemd service allows to export
PDUs status to sidecar

* close issue 14: account manager to declare new slices in /etc/security/access.conf

* rhubarbe load with a non responding CMC now works fine (12)