Incorrect units for metrics

[myllynen]

At least string metrics have wrong units:

$ pminfo -dmtT mmv.test.java.runtime_name

mmv.test.java.runtime_name PMID: 70.3154.734 [An internal Java process identifier]
    Data Type: string  InDom: PM_INDOM_NULL 0xffffffff
    Semantics: discrete  Units: count
Help:
An internal Java process identifier
$ 

There was also discussion whether using unsigned integers/longs should be considered at for counters and other metrics which can only be positive; with Java 8 and Guava this should be possible but it's debatable whether this kind of change would be worth the effort (unlike with the above string example where units should certainly be corrected).