Renamed test to question, updated DB.

Renamed the following:
TestModel.php -> QuestionModel.php
test table in DB -> test_questions
test_id field in test_questions -> question_id
and all the places where they are used.
Added one more question to DB, and updated dbSQL.sql

Problems which I believe where existent before this commit too:
Adding questions pops up a JS alert "Fail." - they are added to the DB
but without the correct answer and without proper unicode support.
Filling tests gets to "Object not found!"
"http://localhost/IExam/not_allowed_user.php"
dbSQL.sql

Small changes.