Add support for one and two finger physical clicks This CL adds support for one and two finger physical clicks. This is done by adding a Click() method to the touchbot class, and the appropriate gesture_interpreter functions. BUG=chromium:474709 TEST=manual Change-Id: I4aed0ebfffc248a0d2f249be47b34af49d5d6876 Signed-off-by: Charlie Mooney <charliemooney@chromium.org> Reviewed-on: https://chromium-review.googlesource.com/277062 Reviewed-by: Shyh-In Hwang <josephsih@chromium.org>