5065efd3 incorrectly changed to doing an rmtree of the entire target
since that was what editionify needed. Editionify should clean the
target directory, but the single HTML file build should not (it ended up
wiping my git repository from my hard drive). We might wish to revisit
this particular fix in the future since it still fails to delete removed
extimages, but this doesn't seem like a big deal.
Better for people to set up their own scheme if they want one, and it
avoids tiddlers potentially being in two different places (since
FileSystemPaths isn't honored during an init/savewikifolder).
The interface isn't the cleanest (it'd probably be better to map from
tiddlers to a set of fields, rather than having a different set of
mappings for each field), but it will do for now. Needing more
than a few of these is a Zettelkasten-design smell anyway.
