To snap things to the grid, just hold control. Control can be set to either do magnetic snapping or incremental snapping, which can be toggled with shift-tab. I think that in this file it's set by default to magnetic snapping, because it makes it way easier to align blocks precisely.
By the way, I've added torches and chests and furnaces and the like now.
I must admit the commands are relatively crappy. Now I'm in skeleton mode, and pressing Z only changes the bone : can't get back to normal body.
Edit : nevermind, that's solved.Also, how the hell can I spin the camera ?
I've kept these things on separate layers for that very reason. Hide the bone layer if you wish to edit the body mesh. The camera can be transformed like any other object, so if you're having trouble with basic transformations, go see some beginner tutorials on Blender.