security: Support ECDSA verification in all related classes.

This commit also addresses some old issues, such as "using namespace std".

Change-Id: I62b8ff97fb2b6f6cfe04b0ad5866bc0797e6e43b
Refs: #1660
diff --git a/src/util/command-interest-validator.hpp b/src/util/command-interest-validator.hpp
index 9d8660e..7d179a0 100644
--- a/src/util/command-interest-validator.hpp
+++ b/src/util/command-interest-validator.hpp
@@ -168,7 +168,7 @@
       Signature signature(interestName[POS_SIG_INFO].blockFromValue(),
                           interestName[POS_SIG_VALUE].blockFromValue());
 
-      if (signature.getType() != Signature::Sha256WithRsa)
+      if (signature.getType() != Tlv::SignatureSha256WithRsa)
         return onValidationFailed(interest.shared_from_this(),
                                   "Require SignatureSha256WithRsa");