Add Prometheus Dell hardware exporter

[dougszumski]

Adds a Prometheus exporter for Dell hardware components. Metrics such
as chassis battery level, fan speed, power consumption, temperature
and hardware status are reported.

[dougszumski]

We need Dell omreport for this to work. To get that it looks like we need to install this:

https://www.dell.com/support/home/uk/en/ukbsdt1/drivers/driversdetails?driverid=xvh5c&oscode=rhe70&productcode=poweredge-r630

I'm not sure about the legal implications of bundling ompreport into the docker image. It seems safer to just install it onto the host, perhaps via a kayobe custom playbook, and then let the container use it from the host.