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/public-key.hpp b/src/security/public-key.hpp
index 7774755..4a8f16a 100644
--- a/src/security/public-key.hpp
+++ b/src/security/public-key.hpp
@@ -16,7 +16,8 @@
 
 namespace ndn {
 
-class PublicKey {
+class PublicKey
+{
 public:
   class Error : public std::runtime_error
   {