Add some magic to collecty that makes the graph templates smaller

Add some magic to collecty that makes the graph templates smaller

This patch will automatically add DEFs for all DSes in a
RR database. For all DEFs and CDEFs will be VDEFs generated
with the current, minimum and maximum values.

That reduces the size of the RRD graph templates massively
and makes them better readable and editable.

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>