Add MBC3 timer

[squidboylan]

MBC3 cartridges can have a timer, current implementation does not implement the timer and instead always says that the timer has 0 for all fields (second, minute, day, etc), this of course has many issues and breaks some games that rely on it for things like a day and night cycle. The MBC3 timer also needs a way to be saved and to be restored the next time the game is played. This is important to simulate time passing while the system is "off"