@variable and @constraint macros are very slow when defining over sets in v0.6

[dlcole3]

The @variable and constraint macros seem really slow under the new version of Plasmo when defining over sets. For example, the last line below in Plasmo v0.5.4 runs in <0.1 seconds, but it runs in >5 seconds in Plasmo v0.6.1.

using Plasmo, JuMP

g = OptiGraph()

X = 100
Y = 100

@optinode(g, n)
@time @variable(n, x[1:X, 1:Y] >= 0);

Perhaps it has something to do with how the names are set. When I run the code below, it takes approximately the same amount of time in both v0.5.4 and v0.6.1.

@time begin
    for i in 1:X
        for j in 1:Y
            @variable(n)     
        end
    end
end

I believe the same problem arises with constraints based on some other code I am running.

[jalving]

should be fixed by #116