#15 Walk-through mode bugs

[Ben Supnik]

Default Walk-through camera position
Defaults to (0,0,0). This tends to be the wrong place. I'm thinking several (scaled) feet back from the front center of the model, at minifigure eye level, would be a better choice.

Scroll position after switch out of walk-through
Switch to walkthrough.
Switch back to 3D perspective.
Horizontal scroll position is all the way left. Should be centered.

Walkthrough camera controls
I would like this to work like a first-person shooter. Up and down for forward and backward, Left and Right for pivot in place. Presumably modifiers for levitate/sink and gaze up/down. Also there could be a time-based curve for controlling speed based on how long you've been holding the arrow key.