HigherPower - More Superclassing

Once I started moving all directional functionality into a common superclass, I couldn't stop.  Today, I ripped out a few more instances of onPlacedBy and determineOrientation from new subclasses of _HPBlockContainer.  I might have caused some issues with the furnace sensor, but I need to do more testing to make sure everything's OK.  I also added the possibility of a nonorientable block to the constructor of _HPBlockContainer for the Lawn Mower and Absorber.  Unfortunately, my recent modifications to the Lawn Mower's Container results in the client being able to open a blank GUI for it when it's moving.  I'm thinking about using block metadata to determine whether the GUI can be opened by right-clicking.