docs: Extending documentation and manpages

Refs: #1462

Change-Id: If33a0f3c623daf3502ed301bcdc63892779463e3
diff --git a/docs/manpages/ndnsec-sign-req.rst b/docs/manpages/ndnsec-sign-req.rst
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+ndnsec-sign-req
+===============
+
+``ndnsec-sign-req`` is a tool to generate a signing request for a particular key.
+
+Usage
+-----
+
+::
+
+    $ ndnsec-sign-req [-h] [-k] name
+
+Description
+-----------
+
+The signing request of a key is actually a self-signed certificate. Given key's information,
+``ndnsec-sign-req`` looks up the key in PIB. If such a key exists, a self-signed certificate of the
+key, or its signing request, will be outputed to **stdout** with base64 encoding.
+
+By default, ``name`` is interpreted as an identity name. ``ndnsec-sign-req`` will generate a
+signing request for the identity's default key.
+
+Options
+-------
+
+``-k``
+  Interpret ``name`` as a key name.
+
+Examples
+--------
+
+Create a signing request for an identity's default key.
+
+::
+
+    $ ndnsec-sign-req /ndn/test/david
+    Bv0DAAc9CANuZG4IBHRlc3QIBWRhdmlkCANLRVkIEWtzay0xMzk2OTk4Mzg5MjU3
+    CAdJRC1DRVJUCAgAAAFFZ+ibohQDGAECFf0BeDCCAXQwIhgPMjAxNDA0MTYwMDIx
+    MDhaGA8yMDM0MDQxMTAwMjEwOFowKjAoBgNVBCkTIS9uZG4vdGVzdC9kYXZpZC9r
+    c2stMTM5Njk5ODM4OTI1NzCCASAwDQYJKoZIhvcNAQEBBQADggENADCCAQgCggEB
+    AKOhGgpUZXiUkaqgfcIvBKSw4wFcSMhBdXr45Tzh8hi8dv1plXKAV4YQLkjHhJqi
+    VTj8qGWkvaP0Kv/mkynaa2rPzUQ77wE1ydRIBUik62bXQa8SanJsV9ux99t9LBKq
+    MY4mtWgal48wFqwqRPNH4xq0yFACh28eaMCMpNvZd2Fh4gmDvQ5xU7sJTyRLt/Mc
+    mfYppDFGfzUP2nP8eQW5I9+L0DXMAAb4z8w1nXHs21xyPv0SSaJXgBH0ZdBwB++D
+    Eo5RLmcDdhFqN0f9Rlz06LVq+gLUC2M+N54jD5qUhPEdW5erY6pyYhq4Zv2B4lbK
+    Zgf2FWIB2iw0of4snf2SxDcCAREWOhsBARw1BzMIA25kbggEdGVzdAgFZGF2aWQI
+    A0tFWQgRa3NrLTEzOTY5OTgzODkyNTcIB0lELUNFUlQX/QEABe8tCY99uFTPyiNX
+    u/hUY96FGnfQx4usA2rCd+M4bkvsAwKQVlbBx1sDXsakvoHhLaCi+MTwHw17o+oG
+    mtPqklLjM8XS+gF+Lh+OyivJQixb8KR8tAtlGeLDoLU/kpgYv/xVhp8Q5ma0/T47
+    faI4Sn6bQP7YoWj+BdO3oZYthtq3MZPw2hl7wuTRMHNm5i3efnZyZdoPNMR2K43x
+    gH6ew1JbEQG7G6l5Q/jjnfT/oTtUeQzqWf2SSylAX+9xFZ9KG4+S6K7mYieBoqiA
+    0wHjvDS1cuIH2j6XveoUYapRjZXaEZqB/YoBwRqEYq2KVn/ol5knLM6FIISXXjxn
+    cIh62A==
+
+
+Create a signing request for a particular key.
+
+::
+
+    $ ndnsec-sign-req -k /ndn/test/david/ksk-1396913058196
+    Bv0DAAc9CANuZG4IBHRlc3QIBWRhdmlkCANLRVkIEWtzay0xMzk2OTEzMDU4MTk2
+    CAdJRC1DRVJUCAgAAAFFZ+mbhRQDGAECFf0BeDCCAXQwIhgPMjAxNDA0MTYwMDIy
+    MTRaGA8yMDM0MDQxMTAwMjIxNFowKjAoBgNVBCkTIS9uZG4vdGVzdC9kYXZpZC9r
+    c2stMTM5NjkxMzA1ODE5NjCCASAwDQYJKoZIhvcNAQEBBQADggENADCCAQgCggEB
+    ALS6udLacpydecxMRIfZeo74fxzpsITqaa/4UxD2FJ9lU4dtfiSSIOaRwAB/w0K/
+    AauQRq3Q1AiEocUsW2h8LmtcuF4Cj9TGAUD/1s3CISMwf9zwQ3ZhNIzN0IOsrpPA
+    TsHrbdwtOxrcFvXX4GnMLWgtvcSB52Cn68h/4AUiA1CG9/DOyCyA4EHiIkHBxh6B
+    TvAmw7SmNjr1ZBTYMaMAEV5/oLZCHzHRO+2fKdEttaWH3bz7iKVVS8u5ZxXcBs8g
+    ot55m7Xf6/TUk3qQXM1kM8wW04U+8n3jch1i7tD2T3c/OFKTT7AWndwcfbU99Z6C
+    FZ7fMsgRHxFNY8hCFZJvFFUCAREWOhsBARw1BzMIA25kbggEdGVzdAgFZGF2aWQI
+    A0tFWQgRa3NrLTEzOTY5MTMwNTgxOTYIB0lELUNFUlQX/QEAkA2DjqDq8pcAD579
+    PaGz3sybCMo2zyjAJvLCRRDPrjQfkublIvN3wGykfsYRKTPW/aDlZcgOtqn8+Qdo
+    tpL9PixqB7hPAZzelADB7Rrqw41p5VNJTzBuIzC6bCssMa8xb2VTGkw1oEtWb1vl
+    Dn+WWvmTNE/yTnSTjNXnTdLinBSA1HH4edkjvH9hTn5+DVyZlpZrTX2qRYcNZqdC
+    kgESIroeoFnp95NVmO+jtL/pKaJ53jh7pvpv7y8wOu28Qk6HuhwDUR186Y/TNNt4
+    hIc0NNDfvvyGgbDEGCMJ7/qOSt0qpJ2BxvPCb9S/bQD1odjGfP2F4ZA2S/JN2SYm
+    5gldDQ==