MET AVG: Fix source scripts to include forgotten variables

The legacy JSP scripts to derive min/max do not often include all variables, we need to improve that.

Also, not every variable or measurable needs to be derived as

Let's list here inconsistencies, fix them when approp.
there may be more thus far (at Exem).

COHM ICET missing the 50cm stats.
CAAM RH stats leave out 3m stats.
CAAM ICET does not compute NEW icet temps stats.
BRHM AIRT may need to include 1m