Integrate FUES EGM

[sbenthall]

A general algorithm for fast upper envelope scan (FUES) EGM is here:

https://github.com/akshayshanker/FUES_EGM

It would make sense to integrate this algorithm as an option to HARK.

(Since the algorithm is general, it would probably be best if connected to a general model form, such as BARK or DARK.)