Error message when a Pin is already in use

[Jaqster]

This would help improve usability. It's not obvious today that when you are using a Pin for capacitive touch (When D0 Pressed), you can't also use it to display lights (Set D0 On). Would be great if we could somehow detect that a Pin is already being used for something else, and show an error message to the user, or grey out that menu option from being selected again.