Curvefit with bounds

[ArnoStrouwen]

I believe the Curvefit option currently does not support bounds on the fitted parameters.

[ChrisRackauckas]

NonlinearSolve.jl now does support bounds, as does CurveFit.jl.

[sathvikbhagavan]

The current implementation of Curvefit - https://github.com/SciML/DataInterpolations.jl/blob/master/ext/DataInterpolationsOptimExt.jl#L34 uses Optim.jl. Maybe we should switch to CurveFit.jl?

[ChrisRackauckas]

Yes that would be more robust.