Attributed relational graphs for cell segmentation

From an [ImageJ forum thread](http://forum.imagej.net/t/cell-nucleus-segmentation/2116):

> There is an interesting procedure to segment clustered nuclei in fluorescence images: http://www.doc.ic.ac.uk/~sa1013/argraphs.html

The source is on GitHub at [sarslancs/argraphs](https://github.com/sarslancs/argraphs).

We could consider doing a language translation of this work to Ops, if anyone has a concrete use case for it.

Start by reviewing the linked ImageJ forum discussion and the sarslancs/argraphs source to understand the proposed clustered-nuclei segmentation method. The issue names no target files or tests; progress would require a concrete use case and an agreed scope for translating the work to ImageJ Ops.

Written by the indexing model from the issue text.