mdw-crypto: Major overhaul.

  * Remove entries which are available in Nelson Beebe's enormous
    collection, or refer to ePrint articles.  There's a file, remapping,
    which explains how to modify documents so that they catch up.

  * Maintain the file using Emacs's capable BibTeX-mode.  In particular,
    this makes sure that the formatting is consistent and arranges that
    the entries are in alphabetical order.