Particular changes:
- looks for *any* endcode, not just [00 FF] (there are other ones, such
as [80 FF])
- updates the text box if an endcode is appended
- feature disabled when called from the timer event (don't want to
insert endcodes while you're in the middle of working block; should only
happen when you save or navigate away)
- multiple insertions will now stack in the status bar