Fixed a few typos in QuestionLinearDependence.aspx for the answer texts. Altered CreateAssignment.aspx to not allow for assigning of impossible problems (independent with more columns than rows). Added a missing case in generating dependent matrices with more columns than rows. Created a new method in MatrixBuilder.cs (checkColumnEquality) to use with the first matrix in grading to ensure every vector is there regardless of order (though I don't anticipate many people actually swapping them as it's much more difficult to keep track of when copying the problem).