Touch pad improvements.

Bug: 4124987

Only show one spot per touch point instead of one spot per
finger for multitouch gestures.

Tweaked the pointer acceleration curves.

Dissociated the hover/tap timeouts from the "tap" timeout
since they mean very different things.

Change-Id: I7c2cbd30feeb65ebc12f6c7e33a67dc9a9f59d4c