doc: Added multiple TODOs for inclusion in the HOWTO

* Some instructions to include are fairly obvious; as with encryption,
  decryption and signature verification.
* Some are a little less obvious.
* This includes the requests received to specifically include subkey
  management (adding and revoking subkeys on a primary key that's
  being retained.
* Added the UID equivalents to the list, as well as key selection
  matters (and may or may not include something for handling group
  lines since that involves wrapping a CLI binary).
* Key control documentation and examples requested by Mike Ingle of
  confidantmail.org.

lang/python/docs/TODO.org

@@ -28,11 +28,13 @@
    to produce reST versions via Pandoc and DITA XML can be reached
    through converting to either Markdown or XHTML first.
 
-** TODO Documentation HOWTO
+** STARTED Documentation HOWTO
    :PROPERTIES:
    :CUSTOM_ID: todo-docs-howto
    :END:
 
+   - State "STARTED"    from "TODO"       [2018-03-08 Thu 13:59] \\
+     Started yesterday.
    Write a HOWTO style guide for the current Python bindings.
 
 *** DONE Start python bindings HOWTO
@@ -41,6 +43,46 @@
     :CUSTOM_ID: howto-start
     :END:
 
+*** TODO Include certain specific instructions in the HOWTO
+    :PROPERTIES:
+    :CUSTOM_ID: howto-requests
+    :END:
+
+    Some functions can be worked out from the handful of examples
+    available, but many more can't and I've already begun receiving
+    requests for certain functions to be explained.
+
+**** TODO Standard scenarios
+     :PROPERTIES:
+     :CUSTOM_ID: howto-the-basics
+     :END:
+
+     What everyone expects: encryption, decryption, signing and verifying.
+
+**** TODO Key control
+     :PROPERTIES:
+     :CUSTOM_ID: howto-key-control
+     :END:
+
+     Generating keys, adding subkeys, revoking subkeys (and keeping
+     the cert key), adding and revoking UIDs, signing/certifying keys.
+
+**** TODO Key control
+     :PROPERTIES:
+     :CUSTOM_ID: howto-key-selection
+     :END:
+
+     Selecting keys to encrypt to or manipulate in other ways (e.g. as
+     with key control or the basics).
+
+**** TODO S/MIME
+     :PROPERTIES:
+     :CUSTOM_ID: howto-s-mime
+     :END:
+
+     Eventually add some of this, but it the OpenPGP details are far
+     more important at the moment.
+
 ** TODO Documentation SWIG
    :PROPERTIES:
    :CUSTOM_ID: todo-docs-swig