Move app/sql/* files to sql/ directory.

sql/connection.h

Index: sql/connection.h
diff --git a/app/sql/connection.h b/sql/connection.h
similarity index 99%
rename from app/sql/connection.h
rename to sql/connection.h
index d82b8b847796716dd8e0fa96320c82d640ae2454..5807e36361ff200445f2d5321d5350bd5d747a42 100644
--- a/app/sql/connection.h
+++ b/sql/connection.h
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef APP_SQL_CONNECTION_H_
-#define APP_SQL_CONNECTION_H_
+#ifndef SQL_CONNECTION_H_
+#define SQL_CONNECTION_H_
 #pragma once
 
 #include <map>
@@ -384,4 +384,4 @@ class Connection {
 
 }  // namespace sql
 
-#endif  // APP_SQL_CONNECTION_H_
+#endif  // SQL_CONNECTION_H_