Save not synced answers in local storage

[hodak]

Exam solver works offline: when you load exam and lose internet connection, you can still solve the exam and once you regain internet connection, your answers will be synced.

Problem is that answers are saved in memory, so after closing browser before answers are synced, they will be gone.

It would be best if answers were stored in local storage and after proper sync local storage would be emptied (sync function)

Also, in this case, it would be important to "merge" user answers from local storage and database when entering the exam solver page (the init function)