EntertainmentGather your “Dallas” friends, plan your barbeque.  The season finale of TV’s No. 1 new cable drama of 2012 gets unveiled Wednesday (8/8) and I can promise you a wealth of captivating  moments. Having watched the first batch of seven episodes together last spring, my mother, who is 81, and daughter, who is 20, and I reconvened to view the season ender, “Revelations.”  Once again, laughing in surprise and shouting at the TV ensued, from all three generations. There’s a …