Add flag to aos_dump and log_cat to print integers in hex format.

Define new --use_hex flag on aos_dump and log_cat applications that
controls how integers are formatted in the output.
Add use_hex field to JsonOptions struct used by FlatbufferToJson.
Update internal helpers used by FlatbufferToJson to act on new tag.

Change-Id: I26dea2cc37de3af4a1e10852e0df8ff93a696802
Signed-off-by: Austin Schuh <austin.schuh@bluerivertech.com>
diff --git a/aos/aos_dump.cc b/aos/aos_dump.cc
index 2fe4955..86f4305 100644
--- a/aos/aos_dump.cc
+++ b/aos/aos_dump.cc
@@ -26,6 +26,7 @@
 DEFINE_int32(timeout, -1,
              "The max time in milliseconds to wait for messages before "
              "exiting.  -1 means forever, 0 means don't wait.");
+DEFINE_bool(use_hex, false, "Are integers in the messages printed in hex notation.");
 
 namespace {
 
@@ -48,7 +49,7 @@
   aos::FlatbufferToJson(
       builder, channel->schema(), static_cast<const uint8_t *>(context.data),
       {FLAGS_pretty, static_cast<size_t>(FLAGS_max_vector_size),
-       FLAGS_pretty_max});
+       FLAGS_pretty_max, FLAGS_use_hex});
 
   if (FLAGS_print_timestamps) {
     if (context.monotonic_remote_time != context.monotonic_event_time) {