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/validator-config.cpp b/src/security/validator-config.cpp
index 4589d82..b9b1bed 100644
--- a/src/security/validator-config.cpp
+++ b/src/security/validator-config.cpp
@@ -490,13 +490,9 @@
       Signature signature(interestName[signed_interest::POS_SIG_INFO].blockFromValue(),
                           interestName[signed_interest::POS_SIG_VALUE].blockFromValue());
 
-      if (signature.getType() != Signature::Sha256WithRsa)
-        return onValidationFailed(interest.shared_from_this(),
-                                  "Require SignatureSha256WithRsa");
+      SignatureWithPublicKey publicKeySig(signature);
 
-      SignatureSha256WithRsa sig(signature);
-
-      const KeyLocator& keyLocator = sig.getKeyLocator();
+      const KeyLocator& keyLocator = publicKeySig.getKeyLocator();
 
       if (keyLocator.getType() != KeyLocator::KeyLocator_Name)
         return onValidationFailed(interest.shared_from_this(),
@@ -527,7 +523,7 @@
       if (checkResult == 0)
         {
           checkSignature<Interest, OnInterestValidated, OnInterestValidationFailed>
-            (interest, signature, nSteps,
+            (interest, publicKeySig, nSteps,
              bind(&ValidatorConfig::checkTimestamp, this, _1,
                   keyName, onValidated, onValidationFailed),
              onValidationFailed,