improve multiple-answer syntax

[Glotzbach]

As stated in this question (https://answers.launchpad.net/openteacher/+question/272038), the syntax to indicate multiple correct answers doesn't work as expected.

* Requiring multiple answers
Question = "1. one 2. second-option" or "1 one 2 second-option"
Expected answer requirements; all strings are present without regards to their order or their delineation (comma, space, semi-column) and spelled correctly in the answer
Now, leaving out the numbers and/or changing the order leads to an incorrect answer.

* Multiple answers are correct
Question = "one, second-option"
Expected answer requirements; either, some or all of the strings (as delineated in the question by commas or semi-columns) should be present and spelled correctly in the answer
Now, this seems to work as a syntax partly; picking either is counted as correct. However, when both answers are given but without a comma or in another order, the answer is counted as incorrect.