Fix the interaction between the checked and checkedValue bindings (see #954)
Modify checked binding slightly so that updating the checkedValue value to match the current checked model value will *check* the checkbox/radio.
Non-behavior-altering refactoring to help clarify how this works
Fix some comments.
Merge pull request #954 from knockout/954-checkedValue-update

Change checkedValue/checked bindings to update value of selection instead of selection