Automatically Detect Incorrect Ordering

[b-camphart]

Related to #22 , if we understand the "direction" being used (based on the arrow direction), then the plugin could also potentially detect if a note breaks continuity. If Note A "points" to Note B, meaning that it leads into Note B and thus Note B must come after Note A, but Note A has a greater value for the current ordering than Note B, we can detect that incongruity and display some kind of warning.