Add HS211 (#346)

* Add HS211

src/ADNLPProblems/hs211.jl

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+export hs211
+
+function hs211(; n::Int = default_nvar, type::Type{T} = Float64, kwargs...) where {T}
+  f(x) = 100*(x[2] - x[1]^3)^2 + (1 - x[1])^2
+  x0 = T[-1.2, 1.]
+  nlp = ADNLPModels.ADNLPModel(f, x0, name = "hs211"; kwargs...)
+  return nlp
+end

src/Meta/hs211.jl

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+hs211_meta = Dict(
+  :nvar => 2,
+  :variable_nvar => false,
+  :ncon => 0,
+  :variable_ncon => false,
+  :minimize => true,
+  :name => "hs211",
+  :has_equalities_only => false,
+  :has_inequalities_only => false,
+  :has_bounds => false,
+  :has_fixed_variables => false,
+  :objtype => :other,
+  :contype => :unconstrained,
+  :best_known_lower_bound => -Inf,
+  :best_known_upper_bound => 750.0,
+  :is_feasible => true,
+  :defined_everywhere => missing,
+  :origin => :unknown,
+)
+get_hs211_nvar(; n::Integer = default_nvar, kwargs...) = 2
+get_hs211_ncon(; n::Integer = default_nvar, kwargs...) = 0
+get_hs211_nlin(; n::Integer = default_nvar, kwargs...) = 0
+get_hs211_nnln(; n::Integer = default_nvar, kwargs...) = 0
+get_hs211_nequ(; n::Integer = default_nvar, kwargs...) = 0
+get_hs211_nineq(; n::Integer = default_nvar, kwargs...) = 0

src/PureJuMP/hs211.jl

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+# Hock and Schittkowski problem number 211.
+#
+#   Source:
+#   Problem 211 in
+#   K. Schittkowski,
+#   More Test Examples for Nonlinear Programming Codes,
+#   Lectures Notes in Economics and Mathematical Systems 282,
+#   Springer Verlag, Heidelberg, 1987.
+#
+export hs211
+
+"HS211 model"
+function hs211(; n::Int = default_nvar, kwargs...)
+  nlp = Model()
+  @variable(nlp, x1, start = -1.2)
+  @variable(nlp, x2, start = 1)
+
+  @objective(nlp, Min, 100*(x2 - x1^3)^2 + (1 - x1)^2)
+  return nlp
+end