-------------
* Improved error checks in ipopt wrapper, and added derivative_test and hessian approx option.
* Added linear_solver and print_level options for ipopt.
* IQP allows general problem as input, forms QP approximation.
* Naive, but hopefully efficient interior-point nonlinear programming solver (inlp) based on taking newton steps on the KKT conditions.
* Improved obj scaling of IQP (to match that of INLP).
* Improved bound stretching in AugL for problems with non-empty interior.