[#179] Make compatible with IterativeSolvers v0.9+

[migarstka]

• Fix a breaking change in IterativeSolvers API
• Add information to docs about which version of IterativeSolvers to use
• Add version constraint to Project.toml

(as discussed in this issue)

MWE:

using COSMO, SparseArrays, LinearAlgebra, Test
using IterativeSolvers, LinearMaps

q = [1; 1.];
P = sparse([4. 1; 1 2]);
A = [1. 1; 1 0; 0 1];
l = [1.; 0; 0];
u = [1; 0.7; 0.7];


Aa = [-A; A]
ba = [u; -l]
constraint1 = COSMO.Constraint(Aa, ba, COSMO.Nonnegatives);

# use CGIndirectKKTSolver here
settings = COSMO.Settings(verbose=true, kkt_solver = CGIndirectKKTSolver)
model = COSMO.Model();
assemble!(model, P, q, constraint1, settings = settings);
res = COSMO.optimize!(model);


@testset "QP Problem" begin
  @test norm(res.x[1:2] - [0.3; 0.7], Inf) < 1e-3
  @test abs(res.obj_val - 1.88) < 1e-3
end
nothing