security: Reorganizing source code to prepare for support of two version of NDN certificates

This commit also removes unused ndn_digestSha256 function and deprecates
crypto::sha256 in favor of crypto::computeSha256Digest in util/crypto.hpp.

Change-Id: I24ee50ff073a96b868633bdf2cfade412d3605f3
Refs: #3098
diff --git a/tests/unit-tests/security/signature-sha256-with-ecdsa.t.cpp b/tests/unit-tests/security/signature-sha256-with-ecdsa.t.cpp
index 648af1d..e6bd97f 100644
--- a/tests/unit-tests/security/signature-sha256-with-ecdsa.t.cpp
+++ b/tests/unit-tests/security/signature-sha256-with-ecdsa.t.cpp
@@ -107,7 +107,7 @@
 {
   Name identityName("/SecurityTestSignatureSha256WithEcdsa/DataSignature");
   BOOST_REQUIRE(addIdentity(identityName, EcdsaKeyParams()));
-  shared_ptr<PublicKey> publicKey;
+  shared_ptr<security::v1::PublicKey> publicKey;
   BOOST_REQUIRE_NO_THROW(publicKey = m_keyChain.getPublicKeyFromTpm(
     m_keyChain.getDefaultKeyNameForIdentity(identityName)));
 
@@ -129,7 +129,7 @@
 {
   Name identityName("/SecurityTestSignatureSha256WithEcdsa/InterestSignature");
   BOOST_REQUIRE(addIdentity(identityName, EcdsaKeyParams()));
-  shared_ptr<PublicKey> publicKey;
+  shared_ptr<security::v1::PublicKey> publicKey;
   BOOST_REQUIRE_NO_THROW(publicKey = m_keyChain.getPublicKeyFromTpm(
     m_keyChain.getDefaultKeyNameForIdentity(identityName)));