Add timestamps to position and behavior events (#147)

* Add timestamps to position events and behaviors.

- Take original event timestamps into consideration so nested tap-holds have proper timing.
- Add position and timestamp to keycode state changed event so the one-shot behavior can properly identify other keypresses and timings.
- Add timestamp to position events received from peripheral

* reduce number of arguments to behaviors

app/include/zmk/behavior.h

@@ -10,4 +10,10 @@ struct zmk_behavior_binding {
     char *behavior_dev;
     u32_t param1;
     u32_t param2;
+};
+
+struct zmk_behavior_binding_event {
+    int layer;
+    u32_t position;
+    s64_t timestamp;
 };