ADMM on LIBBLE-PS

based on http://libble.tk/libble-ps/

TODO

• Replace the gradient descent interface in the Model with alternating direction method of multipliers (ADMM);
• Add grouping strategies to the MPI init stage;
• Implement Trust Region Newton (TRON) Model like LRModel.hpp and SVMModel.hpp;
• Add tests to the project;
• Add configurable-logging to the project instead of std::out;
• Release software artifact as .a files like dmlc/ps-lite;
• (Optional) Integrate whole project with cmake;
• (Optional) Refactor the Python scripts with Yaml or Json configuration;
• (Optional) Replace the Python scripts with Shell scripts;
• TBD.