This final season of Portlandia has been lots of fun, and I’m sure its creators and stars have had lots of fun carrying out one last batch of clever craziness. Take, for example, “Sinkles,” the theme restaurant to make lonely singles feel at home, even when they’re eating out. This theme restaurant doesn’t have tables for one. It has individual working sinks, where diners can stand over to munch morosely on whatever leftovers are brought by the restaurant staffers.