Add a JBLOB renderer

To include ERA data from CERA (inventory#21 (closed)), we'd need something like

for ds in ERA40_SFC06_MM_EWSS ERA40_SFC06_MM_NSSS ; do

    # download using JBlob
    java -cp software/Jblob-2.0.10/Jblob.jar:software/Jblob-2.0.10/commons-codec-1.4.jar \
        de.dkrz.cera.applications.JblobClient \
        --username willi_rath --password XXXXXXXXXX \
        --dataset $ds 

    # convert using CDO
    cdo -t ecmwf -f nc -copy -remapcon,r720x360 -setgridtype,regular ${ds}_1-540.grb ${ds}_1-540.nc
done

and, perhaps, a curl | unzip pipe directly getting Jblob.