Rename/Add files/dirs in blah draft w.r.t comments

comments -> comments.idx (this change also changes the purpose of the
file, the original plan was to just append a new comment to the end of
the comment file, but this newly planned way will make it possible to
have threaded comments

- -> comments.d (new directory for storing comments in)

Each file will get its own comment, filename syntax will be:

<recieptDate>_<normalizedEmailAddress>.txt