quiz 6.x-4.0-rc8

Changes since DRUPAL-6--4-0-RC7:

• API improvement, relative_max_score added to question lists returned from quiz_build_question_list
• Avoid storing invalid results
• If back button is pushed make sure quiz is set to use backwards navigation
• Added ids to the current and total question numbers on the quiz taking page
• Improved update path for multichoice
• #855192 by djdevin: Fixed bug with long and short answer not accepting 0 as an answer
• #858272 by xMATTx: Fixed bug where drupal_add_js wasn't used to add javascript
• #867920 reported by underoathosx: Fixed problem with open and close dates reverting back when questions are saved