Add Get-ClusterStats

Courtesty of
http://tenthirtyam.org/per-cluster-cpu-and-memory-utilization-and-capacity-metrics-with-powercli/.
Only changes are for baseline linting.
Linted Get-ClusterStats

Brings linting to Get-ClusterStats. Proper stops, alignment,
capitalization, and renaming of some variables. Output headers
(NoteProperty) are updated. Repeated calls are saved in variables to
reduce repetitive calls, but there are no functional changes in the
output.