Nelder Mead Threshold

I compared today the implementation of the convergence criterion described by Isabella in sivers-2013 (p.34, eq. 5.15) to the implementation. I believe that there is a square root missing in line 68. I think it should say [...] Math.sqrt(value / dimension) [...] This only affects the chosen threshold. Missing the sqrt, the threshold looks bigger than it is.

@BZoennchen @hm-lehmberg @hm-kleinmei If everyone agrees (and no one finds a mistake in my understanding), I would add the sqrt, so that the threshold is easier to interpret.