More options for camera control

[tallakt]

I know you could do it programatically, but the awkward interface of the OrbitControl is ruining my experience. Could we get some additional controls, eg. by keeping shift pressed while click+drag with the mouse? I'm sure there are some good ways to do this looking either to cad systems or games... In particular I'd like to se:

• move up/down with mouse (ok now)
• move left right with mouse (ok now)
• look around in many direction (ok now)
• move forwards and backwards with mouse (suggest Shift+move up/down)

I'm sure one could expand on this, but just adding that last control would make a huge difference to me.