fix optional edittexts disappearing on backtrack bug

The issue was that when we go from fragment A to fragment B via the continue button, onSaveInstanceState is never called and the information is never stored into a bundle. Therefore, when we return to fragment A on the backstack, the onCreateView is checking an empty bundle. For this case, we create and rely on the two instance variables mDoctorChecked and mChildrenChecked to recreate the state.
more info here: http://stackoverflow.com/questions/11353075/how-can-i-maintain-fragment-state-when-added-to-the-back-stack