Provide dconf keys for: speed, aceleration and acel. threshold for cursor; delay for palettes

[HoboPrimate]

Different devices and different users may need need different values for these settings.
For example, touchpads on high resolution screens will need a higher cursor aceleration with a relatively smallish offset (unlike it's done in OLPC builds), so that you can flick your finger from anywhere on the screen to a corner and activate the frame (tested myself that this is confortable and doable on a XO 1.0 just by configuring these values).
Or >13 year old children who have finer motor skills and longer training with the mouse/touchpad who would take advantage of faster palette pop-ups/pop-downs (as I also have in my current Sugar environment).

Having these configurable as dconf keys would be another step in allowing easy customization of Sugar by individuals and organizations to fit their tastes/devices/users.