Let the Crowbar framework manage Nodes via IPMI

Now that we can detect and configure IPMI, let's start using it!

* Add a slew of IPMI-related attributes for the framework to use.
* Make sure we actually enable LAN access for IPMI commands.
* Add a Power subclasd for the core to use to send power commands
  without it having to know it is using IPMI.
Merge pull request #2 from VictorLowther/add-plugin-for-core-power-management

+2 Let the Crowbar framework manage Nodes via IPMI
Smoked on physical and virtual.
CLI demo worked