Renamed label vars to radio
Tapping Submit Answer button highlights correct choice
Remembered randomized order for each question

Once a question has been loaded at least once, the choices are
never randomized again, to keep the choices from swapping after
the user has selected a choice or submitted the answer.
Fixed bug where answered choices are not highlighted

Since the question only sets the "answered" flag to true
when the user selected a correct choice, answered choices
are not highlighted if user did not selected a choice
or selected an incorrect one.
Fixed bug where wrong choice is highlighted

This was caused because the highlighting of the correct choice
still gets the order from the randomized array, not the one
from that particular object question, hence the order of the
correct choice changes every time the question is loaded.