Improvement: disable multiple column sorting in allocation chart

[talyssonoc]

Right now we allow the user to do multiple-column sorting, a way of composing the sorting algorithm, for example:

1. the user sorts by column A
2. then the user clicks to sort by column B
3. it will result in each "group" formed at step 1 being internally sorted by column B, not the whole table

Even though this is not a bug, I think it would be an improvement to disable this multi-column sorting feature for this table to give it a better UX.