[scikit-image] WIP / Demo: New maxima finding algorithm(s) for 2D (#3022)

Dear devs, I'd like to highlight this pull request https://github.com/scikit-image/scikit-image/pull/3022 as a follow-up of an earlier discussion https://mail.python.org/pipermail/scikit-image/2018-April/005514.html on this mailing list. It demonstrates two new algorithms to find local maxima inside an image. Its performance is comparable to `feature.peak_local_max` but has the same output as `morphology.local_maxima`. Please have a look if you're interested. Best regards, Lars