dvd.h: removed setGenre() method. Not needed.
dvd.cpp: removed setGenre(). Not needed.
dramadvd.h: added signatures and data members.
dramadvd.cpp: added methods and notation
classicsdvd.h: added signatures and data members.
classicsdvd.cpp: added notation and methods.
comedydvd.h: added signatures and datamembers.
comedydvd.cpp: added notation and methods.