Template:Taxobox/displayed cell/doc

Usage
We are passed the *parent* of the taxon in question as a string.
 * If the string is a word (so starts with a letter), the taxon is displayable: return A.
 * If the string is empty, we've hit a top level taxon (e.g. "Life"): return 0.
 * If the taxon in question doesn't have a taxonomy/... page, the string will be " Template:Taxonomy/taxon-in-question ": return X.