removed unused imports - re, render_to_string, hashlib, etc
Updated the code dictionaries
Added new model - Code: first step in model refactoring
add translate_to_code method: takes exam, level, .... and returns its code
new topic in TOPIC_CODE
migration to new models-add code model, add code field to Question and Flashcard, generate and update Question and FlashCard with code
added Code model and code field to Question and FlashCard
changes to convert application to make use of new models from modelremake branch and removal of unused imports
refactor application to make use of new style model definitions
adjustments to templates
added topic counts, added a model attribute
added list to full list of question and flashcard