update restore instance state to avoid 'wrong state class' exception.

[jwmach1]

The current implementation of onRestoreInstanceState causes the following exception. By checking the type of the saved state we avoid this problem and use the superState when necessary. I loosely followed the example from Tricky Android keeping the if condition you started with (as I've done on other custom controls)

Wrong state class, expecting View State but received class com.whygraphics.multilineradiogroup.MultiLineRadioGroup$SavedState instead. This usually happens when two views of different type have the same id in the same hierarchy. This view's id is NO_ID. Make sure other views do not use the same id