Add support for reading, merging, and querying configs

Change-Id: I04a07cf5e9a6b41213b3101f3e04be350e50b41f
diff --git a/aos/util/BUILD b/aos/util/BUILD
index 7b50f49..be6055d 100644
--- a/aos/util/BUILD
+++ b/aos/util/BUILD
@@ -297,6 +297,7 @@
     deps = [
         "//aos/logging",
         "//aos/scoped:scoped_fd",
+        "@com_google_absl//absl/strings",
     ],
 )