* Initial Doxygen configuration along with improvemetns‌ in common.hpp files,
* Extracted gt.hpp and gt/common.hpp files,
* Used using directinve insive common.hpp files.
* Added licence information to Model,
* Added "using" directive usage to Model,
* Improved Doxygen usage in project.
* Slightly improved footer + Sublime Text builders.
* Added licence information and "using" directives to Routines and Program.
* Documentation and using directives in Program, Main and GTL,
* Further improvements of doxygen configuration.
* Repaired errors made during files practices improvement.
* Public API documentation repair.
* Private API documentation repair.