More refactoring

include/asym_field.h

include/asym_field.hpp

include/asym_group.h

include/asym_group.hpp

include/sym_group.hpp

src/asym_field.cpp

src/asym_group.cpp

src/ipre.cpp

src/sym_group.cpp

tests/CMakeLists.txt

tests/test_asym_field.cpp

tests/test_asym_group.cpp

tests/test_group_asym.cpp

tests/test_sym_field.cpp

tests/test_sym_group.cpp

tests/test_sym_matrix.cpp

tests/test_sym_vector.cpp