fix include names

cppcheck isn't smart enough to recognize these are c++ headers, not c
headers.  Considering we're already inconsistent about our naming, it's
easier to just be consistent, and move the last few files to use .hpp
instead of .h.

Tested:
Code builds, no changes.

Signed-off-by: Ed Tanous <ed@tanous.net>
Change-Id: Ic348d695f8527fa4a0ded53f433e1558c319db40
diff --git a/include/persistent_data.hpp b/include/persistent_data.hpp
index 038fcc6..19c424a 100644
--- a/include/persistent_data.hpp
+++ b/include/persistent_data.hpp
@@ -1,13 +1,12 @@
 #pragma once
 
-#include <app.h>
-#include <http_request.h>
-#include <http_response.h>
-
+#include <app.hpp>
 #include <boost/container/flat_map.hpp>
 #include <boost/uuid/uuid.hpp>
 #include <boost/uuid/uuid_generators.hpp>
 #include <boost/uuid/uuid_io.hpp>
+#include <http_request.hpp>
+#include <http_response.hpp>
 #include <nlohmann/json.hpp>
 #include <pam_authenticate.hpp>
 #include <sessions.hpp>