Newton IPM for MDS and support for GPUs

This major release adds

• a Newton interior-point solver for nonlinear nonconvex optimization to complement the existing Quasi-Newton interior-point solver
• capabilities to solve optimization solvers with mixed dense and sparse (MDS) blocks: new MDS interface and new MDS linear algebra
• support for GPU-based acceleration of MDS linear algebra.

Nlp preprocessing/transformations, MAC OS support, and integration with MFEM

Salient developments of this release include

• implementation of various strategies to deal with fixed variables (relax, remove)
• comprehensive testing and bug fixing for Mac OS
• minor fixes of bugs found on various HPC platforms (power pc, bg/q, etc)
• minor interface and options refinement required by the integration with MFEM mesh optimization interface

Initial release

Fully parallel version that has been used in production with external PDE packages for solving topology optimization problems. Has been deployed on a variety of linux-based systems, including HPC platforms.