Returns a string for the edge in the format
{completeness} [nGramPrecision] orthography {bitset} :- category,
where {completeness} and {bitset} are left out if SHOW_COMPLETENESS
is false.
Use this training method if you wish to supply an end of
sentence scanner which provides a different set of ending chars
than the default one, which is "\\.|!|\\?|\\\"|\\)".