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/util/command-interest-validator.hpp b/src/util/command-interest-validator.hpp
index 07e164f..c543549 100644
--- a/src/util/command-interest-validator.hpp
+++ b/src/util/command-interest-validator.hpp
@@ -182,21 +182,21 @@
           timestampIt->second = interestTime;
         }
     }
-  catch (const Tlv::Error& e)
-    {
-      return onValidationFailed(interest.shared_from_this(),
-                                "Cannot decode signature related TLVs");
-    }
-  catch (const Signature::Error& e)
+  catch (Signature::Error& e)
     {
       return onValidationFailed(interest.shared_from_this(),
                                 "No valid signature");
     }
-  catch (const IdentityCertificate::Error& e)
+  catch (IdentityCertificate::Error& e)
     {
       return onValidationFailed(interest.shared_from_this(),
                                 "Cannot locate the signing key");
     }
+  catch (Tlv::Error& e)
+    {
+      return onValidationFailed(interest.shared_from_this(),
+                                "Cannot decode signature related TLVs");
+    }
 
   return onValidated(interest.shared_from_this());
 }