GSS: parameterize by Evaluator and DirectionGen
GSS: parameterize by Evaluator and DirectionGen

- add explicit "evaluator" field

JuliaPackageMirrors/BlackBoxOptim.jl,tkelman/BlackBoxOptim.jl,tkelman/BlackBoxOptim.jl,JuliaPackageMirrors/BlackBoxOptim.jl,multidis/BlackBoxOptim.jl,tkelman/BlackBoxOptim.jl,multidis/BlackBoxOptim.jl,JuliaPackageMirrors/BlackBoxOptim.jl,multidis/BlackBoxOptim.jl