Context condition node : taxonomy with depth

A context condition to support hierarchy matching when looking for tagged nodes

A minor form of contexts node-taxonomy support.

I had a large tree hierarchy of terms, and needed to set the condition "if this term or any under it applied to the current node then ..." (add a special footer block)

I first tried to extend the context.module native plugin that almost does this - but found that in order to toggle the behavior I'd have to change its data schema to capture the extra option.
So instead I forked it a bit and added my extra (10) lines to do this.