Move non-data files to extra-source-files
Tweak some admin files
Do not import nor re-export showT

The 'T' at the end suggests a monad transformer and, anyway,
it's very short to define and people may choose to define
it differently for their varied uses, e.g., taking advantage
of package pretty-show. In minimorph, I think showT should
be renamed, e.g., to tshow.