Title: test for fuzzy answers

With this new feature, you can optionally allow some fuzzyness for the answers. This would e.g. allow you to also accept answers with typos or a similar spelling. Case sensitivity is turned on right now.

In the tasks options, there are some basic parameters for tuning the fuzziness. You can detect fuzzy correct answers by setting the maximum number of displaced characters or by setting a minimum threshold for similarity.

Q: cat [...]

House [...]

mother [...]

deoxyribonucleic acid [...]
A: cat; House; mother; deoxyribonucleic acid