LAS VEGAS-Most smart TVs are pretty stupid. Sure, they give you access to a variety of Internet services, but only through a dumb, pushbutton remote control. At this year’s Consumer Electronics Show, electronics firms are showing off products that’ll bring Kinect-like speech and motion control to millions more TV viewers. A pair of Boston-area companies demonstrated their speech-control software, while two South Korean television titans displayed advanced sets they’re planning to roll out this year.