encoding: update number assignments

This commit declares:

* TLV-TYPEs for typed name components in NDN naming conventions
* SignatureType number for HMAC
* ContentType numbers for Prefix Announcement and FLIC

This commit also:

* Improves stream insertion operator for SignatureTypeValue
* Adds stream insertion operator for ContentTypeValue
* Corrects several references to certificate format spec

refs #4577, #4649

Change-Id: Ibfd5cc1408cf892e38a2be93bf17e76f628f255d
diff --git a/src/security/validity-period.hpp b/src/security/validity-period.hpp
index ee7c602..ba05b7a 100644
--- a/src/security/validity-period.hpp
+++ b/src/security/validity-period.hpp
@@ -32,7 +32,7 @@
 
 
 /** @brief Abstraction of validity period
- *  @sa docs/tutorials/certificate-format.rst
+ *  @sa docs/specs/certificate-format.rst
  */
 class ValidityPeriod
 {