Decide on a better way to handle uncollapsed superposed states

[AgustinVallejo]

Currently, for the 'Basis state' radio buttons to toggle and untoggle freely we are using QuantumUncollapsedCoinStateValues = [ 'up', 'down', 'superposed' ] in addition to the normal 'up' and 'down' in QuantumCoinStateValues. After discussing with @jbphet we agreed that there should be a safer and more elegant way of stating that a coin is in superposition.