add write_data() support to remaining improper styles.

src/USER-MISC/improper_cossq.cpp

src/USER-MISC/improper_cossq.h

src/USER-MISC/improper_distance.cpp

src/USER-MISC/improper_distance.h

src/USER-MISC/improper_fourier.cpp

src/USER-MISC/improper_fourier.h

src/USER-MISC/improper_ring.cpp

src/USER-MISC/improper_ring.h