Use PCP string metrics as labels, if possible

[joehandzik]

Currently, your code skips over string metrics because Prometheus does not deal with non-numeric metrics. Instead, you could investigate some intelligent way to make the data from these string metrics available (as labels, perhaps).

An idea would be to take the string metrics for each "instance" (in PCP terms), drop the instance number as a label, and use the name of the string metric and the string metric data as a label and label value (respectively).