Revised flashcards, modified install profile.

- Added taxonomy and auto_nodetitle to the drush makefile, as well as to the
  install profile.
- Changed some of the entries in the drush makefile to use more updated
  versions of some contrib modules.
- added the "subject" and "difficulty" taxonomies to flashcards.
- configured the flashcard content type to use an automatically generated
  title, with the title field hidden to the user.