adding min-median-max normal period variables for bioclimate variables

[whmacken]

For each of the climr version of the AdaptWest bioclimate variables, generate for each normal period min, median, and max variables.

[cour10eygrace]

these are the worldclim bioclim vars - I checked and except for BIO 1 and BIO 12 (MAT, MAP), the rest of these don't seem to be in climr and so I think we should add

BIO1 = Annual Mean Temperature

BIO2 = Mean Diurnal Range (Mean of monthly (max temp - min temp))**

BIO3 = Isothermality (BIO2/BIO7) (* 100)

BIO4 = Temperature Seasonality (standard deviation *100)

BIO5 = Max Temperature of Warmest Month

BIO6 = Min Temperature of Coldest Month

BIO7 = Temperature Annual Range (BIO5-BIO6)

BIO8 = Mean Temperature of Wettest Quarter

BIO9 = Mean Temperature of Driest Quarter

BIO10 = Mean Temperature of Warmest Quarter

BIO11 = Mean Temperature of Coldest Quarter

BIO12 = Annual Precipitation

BIO13 = Precipitation of Wettest Month

BIO14 = Precipitation of Driest Month

BIO15 = Precipitation Seasonality (Coefficient of Variation)

BIO16 = Precipitation of Wettest Quarter

BIO17 = Precipitation of Driest Quarter

BIO18 = Precipitation of Warmest Quarter

BIO19 = Precipitation of Coldest Quarter

[cour10eygrace]

also @whmacken idea of creating heat drought index e.g. combination of max monthly temp and CMD max thresholds