JuMP 0.21 is released

Despite the name, JuliaOpt has not, in practice, been the organization for “all optimization packages in Julia” for a number of years now. See JuliaNLSolvers · GitHub, https://github.com/JuliaSmoothOptimizers, and https://github.com/kul-forbes among others. Moving to jump-dev is also correcting this misleading impression.

Discoverability is an important issue, and we would like to keep an up-to-date list of optimization-related packages in a highly visible place. The list is currently at Packages and will be moving to jump.dev.