Overhauled sketch

- no longer requires the DigitalToggle library
- screen updates are done more effeciently, only when variables are
  changed - and the check is now done once diectly within the encoder
  reading function, rather than individually within each menu item
- due to more efficient screen updates, lcd.clear can now be used before
  each update, so padding out strings to fill lcd rows is no longer
  necessary
- added mirror lockup support - sends two delay seprated shutter signals