Erik. ShearLayer test implemented. Major cleanup. gengrid1D rewritten.

1) GenGrid1D rewritten, but not tested.
2) Changes in Roe solver, not tested.
3) Added cmake file and .gitignore changed to ignore CMake temporary files.
4) Major clean up. All unused files removed. Grid class get rid of all obsolete fields.
5) Several bug fixes and refactoring.
Erik. LomonosovFortovGasModel implemented for new equation of state of condensed matter (stainless steel, plumbum).
Erik. CGNSReader bug fixes and new element types support.
Erik. New RiemannSolver base class, HLLC solver implemented for general EOS.

1) Also signum function and new file utilityfunctions.h for storing utility functions
Erik. gengrid1D revised, bug fixes.
Erik. Reference point. Running and tested HLLC solution for Sod shock tube test.

1) Some kernel modifications.