Invalid graph templates

I've created a script (see attachments) to use the rrdtool graph command to analyze every single graph template defined on $OPENNMS_HOME/etc/snmp-graph.properties.d, as I saw a couple of errors on some graphs.

Interestingly, I found that around 60 graphs definitions have errors (based on the current content for foundatioon-2016. We should fix those errors in order to render the graphs with RRDtool. It might be possible that this affects JRobin as well (and maybe Backshift).