Improve log_cats raw and fetching capabilities

Make --raw be able to print parsed messages.  Much more useful than just
the headers.

Also, let --fetch control if we print out messages from before the start
of the log file.

Change-Id: I150bad1d5ac5b3caa7f5cab6ff6fe5cb7b4a7f67
diff --git a/aos/configuration.h b/aos/configuration.h
index 9193fd5..ccc6246 100644
--- a/aos/configuration.h
+++ b/aos/configuration.h
@@ -113,6 +113,8 @@
 
 // Prints a channel to json, but without the schema.
 std::string CleanedChannelToString(const Channel *channel);
+// Prints out a channel to json, but only with the name and type.
+std::string StrippedChannelToString(const Channel *channel);
 
 // Returns the node names that this node should be forwarding to.
 std::vector<std::string_view> DestinationNodeNames(const Configuration *config,