Coherent & concise JuMPification of MARGO?

[hdrake]

As mentioned in https://github.com/hdrake/ClimateMARGO.jl/issues/14, it would be nice to reduce the JuMP implementation of MARGO to a few single-line statements like:

for i in N; @constraint{ T(M,R,G,A) < Tstar }; end
@NLobjective( model_optimizer, Min, net_present_cost(M,R,G,A) );

which reuse the diagnostic functions such as T which fully describe the model (see https://github.com/hdrake/ClimateMARGO.jl/tree/updating-structure) but are complicated functions of both the four controls {M,R,G,A} as well as a number of prescribed inputs functions and parameters. In the current implementation https://github.com/hdrake/ClimateMARGO.jl/commit/af16f490a3fa55754cca4738bead7c1877a68064, these optimization constraints are hard-coded from scratch, span many lines, and are repeated several times over.