Another big refactor.  Create a single StatusPoller per device type since different devices have different APIs that need to be called to gather up the necessary status
Yet another refactor: moved some common code out of individual api pollers into modified TetherPoller -> TetherApiPoller.  Added first cut of verizon api pollers.
Added a TestDataList object to make it easy to rotate through test data options for test pollers
I think everything is working now?  I've also added a network-type indicator to the signal strength icon.