Accumulating cutoffs

I've added the ability to accumulate excised cutoffs and display them in the plot. Cutoffs can be kept and 'aged' for a certain number of additional steps, or for forever. (Note that the cutoff plot does not necessarily show the full meandering extent of the river, as the full history of the main stream is not displayed, only the current stream and all past cutoffs.) I've also made several additional enhancements to the simulation program. Here is the current state of the UI:

(Click for larger image)

Here is a montage of a simulation showing all cutoffs for 0, 100, 200, 272, 320, 350, 400, 450, 500, 550, 588, 600, 650, 700, 750, 800, 850, and 900 steps:

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The program appears to be fairly stable now, so I will be returning to work on the JP method for the rest of this month. I hope to fix all of the problems I mentioned last week.