Add remote timestamps and queue_index to context

This gives us the knobs to expose the remote timestamps and queue_index
to anything receiving the events.  The first use case is the logger.  It
can now log forwarded entries *without* having to make the
message_gateway responsible for logging this data.

Change-Id: Ie34dd040d270f4fa90ecd6e463069e1adca1818a
diff --git a/y2018/wpilib_interface.cc b/y2018/wpilib_interface.cc
index 968076d..641a474 100644
--- a/y2018/wpilib_interface.cc
+++ b/y2018/wpilib_interface.cc
@@ -537,7 +537,7 @@
     // Flash the red light slowly.
     StatusLightT color;
     if (!status_light_fetcher_.get() ||
-        monotonic_now > status_light_fetcher_.context().monotonic_sent_time +
+        monotonic_now > status_light_fetcher_.context().monotonic_event_time +
                             chrono::milliseconds(100)) {
       color.red = 0.0;
       color.green = 0.0;
@@ -549,7 +549,7 @@
         color.red = 0.5;
       } else if (!vision_status_fetcher_.get() ||
                  monotonic_now >
-                     vision_status_fetcher_.context().monotonic_sent_time +
+                     vision_status_fetcher_.context().monotonic_event_time +
                          chrono::seconds(1)) {
         color.red = 0.5;
         color.green = 0.5;