Shortanswer resonses should be trimmed before being saved in the database

Shortanswer questions are marked with leading and trailing whitespace stripped off. Therefore, student reposes should be trimmed before they are stored in the database.

We had a student express concern because they seemed to have been marked right for a question they had left blank. In fact, they must have leant on their keyboard, because their answer was hundreds of spaces, then the right answer, so the answer box appeared blank. This is too confusing.