security: Update Signature abstraction to match 0.1.1 spec

This commit removes intermediate SignatureWithPublicKey data
structure.  All uses of such data structure should be replaced with just
Signature and check that KeyLocator is present (hasKeyLocator()).

Change-Id: I1157e05c6a717ea28df91c4bfd76c7145b520a15
Refs: #1750
diff --git a/src/security/validator.hpp b/src/security/validator.hpp
index e9bf37e..9a3b4a3 100644
--- a/src/security/validator.hpp
+++ b/src/security/validator.hpp
@@ -107,7 +107,7 @@
 
   /// @brief Verify the blob using the publicKey against the signature.
   static bool
-  verifySignature(const Buffer& blob, const SignatureWithPublicKey& sig, const PublicKey& publicKey)
+  verifySignature(const Buffer& blob, const Signature& sig, const PublicKey& publicKey)
   {
     return verifySignature(blob.buf(), blob.size(), sig, publicKey);
   }
@@ -115,7 +115,7 @@
   /// @brief Verify the data using the publicKey against the SHA256-RSA signature.
   static bool
   verifySignature(const Data& data,
-                  const SignatureWithPublicKey& sig,
+                  const Signature& sig,
                   const PublicKey& publicKey)
   {
     return verifySignature(data.wireEncode().value(),
@@ -129,7 +129,7 @@
    */
   static bool
   verifySignature(const Interest& interest,
-                  const SignatureWithPublicKey& sig,
+                  const Signature& sig,
                   const PublicKey& publicKey)
   {
     if (interest.getName().size() < 2)
@@ -146,7 +146,7 @@
   static bool
   verifySignature(const uint8_t* buf,
                   const size_t size,
-                  const SignatureWithPublicKey& sig,
+                  const Signature& sig,
                   const PublicKey& publicKey);
 
 
@@ -248,9 +248,6 @@
            const OnInterestValidationFailed& onValidationFailed,
            int nSteps);
 
-  static shared_ptr<SignatureWithPublicKey>
-  determineSignatureWithPublicKey(const Signature& signature);
-
   /// Hooks
 
   /**