v2.1.0 (clean)

== v2.1.0 Mode to display solutions after submission, eval fixes, UI fixes

• Feature: DISPLAY_SOLUTIONS_AFTER_SUBMIT mode, to display questions and solutions after submission, while not allowing changing answers
• Feature: store timestamp of first connection for each student
• Feature: script to evaluate student group files (firebase database dumps)
• Feature: display expected solutions in quizz evaluation report
• Feature: adjust scores based on points per quizz and code coefficient
• Feature: CodeEvaluator's timeout error message can be customized by eval/
• Feature: added _sendOnce() and _log() functions, in code evaluator
• BUG FIX: fixed evaluation script, to match firebase new API (v3)
• UI FIX: allow exam to be printed (or saved as PDF)
• UI FIX: display date of submission, after submission
• UI FIX: fixed qcm/quizz choice selection bug
• UI FIX: ignore TAB from code element, to prevent accidental submission
• UI FIX: added spacing in evaluation reports
  test script
• cleaner file structure