Eliminate network jitter from touch input replay

Add fields to the TouchEvent message to include the client-side
DownTime and EventTime fields.

Also added support for the "Historical" batched form of motion events
where a single Event object contains a series of pointer movements all
batched together.

Finally, added the EdgeFlags field, that could be used for gestures like
"swipe in from edge" used by certain apps.

The new fields are all optional to maintain backwards compatibility with
old clients.

Change-Id: Ie93a25a040eba74dd4f4675b8704f16ad0ccb88a