exceptions: Make Tlv::Error a base class for all packet-processing exceptions

This commit also includes a number of code style fixes.

Change-Id: I44f83915e733b43d5f43b4266902c8262e928d91
Refs: #1528
diff --git a/src/security/certificate-subject-description.hpp b/src/security/certificate-subject-description.hpp
index 7665a3f..e8732f0 100644
--- a/src/security/certificate-subject-description.hpp
+++ b/src/security/certificate-subject-description.hpp
@@ -12,14 +12,17 @@
 #include "../common.hpp"
 #include "../encoding/oid.hpp"
 
-namespace CryptoPP { class BufferedTransformation; }
+namespace CryptoPP {
+class BufferedTransformation;
+}
 
 namespace ndn {
 
 /**
  * A CertificateSubjectDescription represents the SubjectDescription entry in a Certificate.
  */
-class CertificateSubjectDescription {
+class CertificateSubjectDescription
+{
 public:
   CertificateSubjectDescription(CryptoPP::BufferedTransformation& in)
   {