A growing breed of stealthy super PACs using no more than nebulous names and post office boxes are perfecting sophisticated and shady money-moving schemes to keep big-bucks donors hidden and voters in the dark, a Herald investigation reveals.The easy-to-establish political organizations, expected to shake the Massachusetts political landscape this year, have learned to funnel money through different states, different super PACs and sometimes limited liability corporations to evade reporting laws and keep their contributors cloaked.