docs: fix syntax highlighting of code blocks

And various other cleanups

Change-Id: If945f5407036e73db980cafd2185359a488a0ff1
diff --git a/docs/specs/safe-bag.rst b/docs/specs/safe-bag.rst
index fcb6211..23e93cb 100644
--- a/docs/specs/safe-bag.rst
+++ b/docs/specs/safe-bag.rst
@@ -1,24 +1,24 @@
-Export/Import Credentials
-=========================
+SafeBag Format for Exported Credentials
+=======================================
 
 Sometimes, one may need to export credentials (e.g., certificate and private key) from
 one machine, and import them into another machine.  This requires a secured container for
 sensitive information.  We define **SafeBag**, which contains both an NDN certificate
 (:doc:`version 2.0 <certificate-format>`) and the corresponding private
-key which is encrypted in `PKCS#8 format <https://tools.ietf.org/html/rfc5208>`_.
+key, which is encrypted in `PKCS #8 format <https://tools.ietf.org/html/rfc5208>`_.
 
 The format of **SafeBag** is defined as:
 
-::
+.. code-block:: abnf
 
     SafeBag = SAFE-BAG-TYPE TLV-LENGTH
-                CertificateV2   ; a data packet following certificate format spec
+                CertificateV2
                 EncryptedKeyBag
 
     EncryptedKeyBag = ENCRYPTED-KEY-BAG-TYPE TLV-LENGTH
-                        *OCTET ; private key encrypted in PKCS#8 format
+                        *OCTET ; private key encrypted in PKCS #8 format
 
-All TLV-TYPE codes are application specific:
+All TLV-TYPE numbers are application specific:
 
 +---------------------------------------------+-------------------+----------------+
 | TLV-TYPE                                    | Assigned number   | Assigned number|