Merge Neuron(s) function

This is what @lara said 27d ago…hence i am surprised that now we are saying “no unjoin”.

Additionally @lara said that having that flag on a neuron “does not have any effect” on the neuron…clearly currently a community fund cannot be merged… I am not exactly sure why/how these communication gaps exists. I think having a named product manager(who speaks authoratively for the feature) for each major functionality would help tremendously.