Use more C++17 features

Mainly structured bindings, inline variables, and class template
argument deduction, plus many more smaller things.

Change-Id: I810d17e0adb470426e4e30c898e03b3140ad052f
diff --git a/core/common.hpp b/core/common.hpp
index a5f47d9..96d34a7 100644
--- a/core/common.hpp
+++ b/core/common.hpp
@@ -54,6 +54,7 @@
 #include <set>
 #include <stdexcept>
 #include <string>
+#include <string_view>
 #include <utility>
 #include <vector>
 
@@ -93,6 +94,7 @@
 using std::const_pointer_cast;
 
 using namespace std::string_literals;
+using namespace std::string_view_literals;
 
 using ndn::span;
 using ndn::to_string;