security: renaming methods

1. renaming Verifier::policies to Verifier::policy
2. appending SecTpm related methods with "InTpm"

Change-Id: I3790947d3f236e8d56fd52eaefc6e2bbaea92385
diff --git a/include/ndn-cpp/security/verifier.hpp b/include/ndn-cpp/security/verifier.hpp
index 764dcd4..2dbd995 100644
--- a/include/ndn-cpp/security/verifier.hpp
+++ b/include/ndn-cpp/security/verifier.hpp
@@ -43,7 +43,7 @@
    * @return The Policy.
    */
   inline SecPolicy&
-  policies()
+  policy()
   {
     if (!policy_)
       throw Error("policy is not assigned to the KeyChain");