Allow scorers to rescore answers

Problem/Motivation

It's already possible to change the score of short answer and long answer, so a scorer should be able to award a different number of points regardless of the question, in the case that a question was created incorrectly and then answered.

Proposed resolution

Expose the score field for all question types.
Allow the scorer to change the answer.

Remaining tasks

Expose the score field for all question types.
Allow the scorer to change the answer.

User interface changes

API changes