directories stored in resources. On device this is currently
"\Program Files\Crosswords" and "\SD Card". (Just "." for win32.)
Later may need to restrict on the card too. Still to do: make "no
dicts found" Alert list the places searched.
rather than call OpenFile, which doesn't let you browse much of the
file system on CE. Heading for installing dicts in Program Files so
users never have to worry about them.