In 2012, with laptops and desktops to maintain, gaming systems to upgrade, e-readers to configure, pictures to store, music and videos to manage, wireless routers to set up, contacts to migrate, viruses to fight, smart phones to program, apps to download, and parental controls to wrestle with, it’s come to this: every home needs its own tech support. “Remember the good old days?’’ asked MIT professor Randall Davis, “when all you had to do was try to figure out how to set the clock on the VCR?’’