Improved note dragging/dropping for saving and sorting about mpkedit

[bryc]

I removed the note re-order code since I can't find a good way to do it right. It was conflicting with the drag-save method that Chrome supports, and it relied entirely on the note table being rewritten.

Since the parser no longer rewrites the noteTable and attempts to retain the original data, note re-ordering has to be completely rethought to handle both display modes, retain as much data integrity as possible, and not interfere with other drag operations, and be done as elegantly as possible.

[bryc]

A billion years later, and I came up with a simple solution.

1. Add a separate mode which enables reordering, have it off by default. This is fine because reordering is not that important, it's just nice to have.
2. Reorder notes by just swapping them. This avoids all the issues I had before: no need to sanitize or sort the list before reordering. Minimal data changes, and doesn't lose any data, even when swapping to empty slots that contain garbage data. It also avoids 'accidental operations', because no changes occur until you let go on a destination, and leaving the destination will cancel the operation. The visual feedback is also pretty clear.

So all in all, now it's done right, and I can no longer feel guilty that the README lists a feature that doesn't exist. :)