Flickable's physics needs improving

The flick gesture is supposed to draw from the real world, as a metaphor for flicking a sheet of paper. But with Flickable's current default flickDeceleration of 500 the "paper" skids all over the place. To make it less "slippery" the default deceleration needs to be increased to around 3000, and perhaps other tweaks to the physics are needed too, like the amount a long list can overshoot before bouncing back.