Add ConsoleZ to the Windows install script and improve security with SHA1 hashes.

Updates from:

  git://tremily.us/swc-setup-windows-installer bc-namespaced

Inspired by @joonro's [comment][1] in #140, but currently untested.

This PR is against gh-pages, because that's still bc's default branch.  Let me know if it should be against master.

[1]: https://github.com/swcarpentry/bc/issues/140#issuecomment-28314570