Implement UART serialization code to/from the cameras

Also fix a few things in the SPI serialization code I noticed while
reusing the pattern.

Change-Id: I645775b4c9ea1265025957e50b4d03f4932582f8
diff --git a/y2019/jevois/structures.h b/y2019/jevois/structures.h
index 15889c4..fcc268e 100644
--- a/y2019/jevois/structures.h
+++ b/y2019/jevois/structures.h
@@ -107,7 +107,7 @@
 
 // This is all the information sent from the Teensy to each camera.
 struct CameraCalibration {
-  enum class CameraCommand {
+  enum class CameraCommand : char {
     // Stay in normal mode.
     kNormal,
     // Go to camera passthrough mode.
@@ -120,6 +120,15 @@
     if (other.calibration != calibration) {
       return false;
     }
+    if (other.teensy_now != teensy_now) {
+      return false;
+    }
+    if (other.realtime_now != realtime_now) {
+      return false;
+    }
+    if (other.camera_command != camera_command) {
+      return false;
+    }
     return true;
   }
   bool operator!=(const CameraCalibration &other) const {