Migrate to C++17 and refactor

Change-Id: I53407266939258990a1c3a9363c3ebe9ea113fd2
diff --git a/src/name-assignment/assignment-email.cpp b/src/name-assignment/assignment-email.cpp
index 685a820..2cb6184 100644
--- a/src/name-assignment/assignment-email.cpp
+++ b/src/name-assignment/assignment-email.cpp
@@ -22,7 +22,7 @@
 
 namespace ndncert {
 
-NDNCERT_REGISTER_FUNCFACTORY(AssignmentEmail, "email");
+NDNCERT_REGISTER_NAME_ASSIGNMENT_FUNC(AssignmentEmail, "email");
 
 AssignmentEmail::AssignmentEmail(const std::string& format)
   : NameAssignmentFunc(format)