security: CryptoPP functions are used directly to encode/decode DER/BER

This change eliminates the need for custom der decoder/encoder.

Change-Id: I5be2e55cec2b63157927a4ad87fffe8e8651ed3c
diff --git a/include/ndn-cpp/security/certificate/certificate.hpp b/include/ndn-cpp/security/certificate/certificate.hpp
index 025e420..0c7323b 100644
--- a/include/ndn-cpp/security/certificate/certificate.hpp
+++ b/include/ndn-cpp/security/certificate/certificate.hpp
@@ -99,8 +99,8 @@
   const PublicKey& 
   getPublicKeyInfo() const { return key_; }
 
-  virtual Name 
-  getPublicKeyName() const = 0;
+  // virtual Name 
+  // getPublicKeyName() const = 0;
   
   /**
    * Check if the certificate is valid.