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/security/signature-sha256-with-rsa.hpp b/src/security/signature-sha256-with-rsa.hpp
index bd3fd32..fc60248 100644
--- a/src/security/signature-sha256-with-rsa.hpp
+++ b/src/security/signature-sha256-with-rsa.hpp
@@ -51,7 +51,7 @@
   SignatureSha256WithRsa(const Signature& signature)
     : SignatureWithPublicKey(signature)
   {
-    if (getType() != Signature::Sha256WithRsa)
+    if (getType() != Tlv::SignatureSha256WithRsa)
       throw Error("Incorrect signature type");
   }
 };