refactored grid and distributed_matrix

encapsulated member variables of grid and distributed_matrix.
removed virtual functions and inheritance structure from grid.
merge
clean up code

remove verbose tag dispatched member-functions from grid :
calculate_grid_row(int, grid_major_tag) / col(int, grid_major_tag)
Merge pull request #36 from yomichi/grid-refactoring

refactored grid class and distributed_matrix class