Move all fly mode related input handling to FlyModeHelper.

Signed-off-by: Kristian Duske <kristian.duske@gmail.com>
Redo mouse preference pane.

Signed-off-by: Kristian Duske <kristian.duske@gmail.com>
Revise preference dialog and add preferences for fly mode.

Signed-off-by: Kristian Duske <kristian.duske@gmail.com>