Add support for elog callback

Added support for "callback: elog" in PDM.
templates/elog.mako.cpp is used to generate the Elog call.
templates/errors.mako.hpp is used to generate the errors.hpp
used by generated.hpp to include any error.hpp files like
"xyz/openbmc_project/Common/error.hpp"

Change-Id: Id0ae3aca4282095f58a8939b70e398bec706d7f5
Signed-off-by: Gunnar Mills <gmills@us.ibm.com>
diff --git a/src/templates/generated.mako.hpp b/src/templates/generated.mako.hpp
index b8ad523..04f2bde 100644
--- a/src/templates/generated.mako.hpp
+++ b/src/templates/generated.mako.hpp
@@ -8,6 +8,8 @@
 #include "count.hpp"
 #include "data_types.hpp"
 #include "journal.hpp"
+#include "elog.hpp"
+#include "errors.hpp"
 #include "method.hpp"
 #include "propertywatchimpl.hpp"
 #include "sdbusplus.hpp"