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/validation-request.hpp b/src/security/validation-request.hpp
index 8846636..b525c27 100644
--- a/src/security/validation-request.hpp
+++ b/src/security/validation-request.hpp
@@ -27,7 +27,8 @@
                       const std::string&)> OnDataValidationFailed;
 
 
-class ValidationRequest {
+class ValidationRequest
+{
 public:
   ValidationRequest(const Interest& interest,
                     const OnDataValidated& onValidated,