Generalizing types in NarrowBand class.

src/level_set/redistancing_Sussman/HelpFunctionsForGrid.hpp

src/level_set/redistancing_Sussman/NarrowBand.hpp

src/level_set/redistancing_Sussman/RedistancingSussman.hpp

...level_set/redistancing_Sussman/tests/convergence_test.cpp

...t/redistancing_Sussman/tests/help_functions_unit_test.cpp

...l_set/redistancing_Sussman/tests/narrowBand_unit_test.cpp

...istancing_Sussman/tests/redistancingSussman_unit_test.cpp

src/level_set/redistancing_Sussman/tests/test.cpp