docs+tools: improve ndnsec help, error messages, and manual page

Exit with status code 2 on malformed command line

Refs: #3777
Change-Id: Id682a5d69c15c74cfa1903db38b5389936f5be58
diff --git a/docs/conf.py b/docs/conf.py
index 9e76dff..82688a1 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -65,7 +65,7 @@
 
 # General information about the project.
 project = u'ndn-cxx: NDN C++ library with eXperimental eXtensions'
-copyright = u'Copyright (c) 2013-2018 Regents of the University of California.'
+copyright = u'Copyright (c) 2013-2019 Regents of the University of California.'
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.
@@ -239,23 +239,27 @@
 # One entry per manual page. List of tuples
 # (source start file, name, description, authors, manual section).
 man_pages = [
-    ('manpages/ndnsec', 'ndnsec', u'NDN security tools', None, 1),
-    ('manpages/ndnsec-cert-dump',    'ndnsec-cert-dump',   'part of NDN security tools', None, 1),
-    ('manpages/ndnsec-cert-gen',     'ndnsec-cert-gen',    'part of NDN security tools', None, 1),
-    ('manpages/ndnsec-cert-install', 'ndnsec-cert-instal', 'part of NDN security tools', None, 1),
-    ('manpages/ndnsec-delete',       'ndnsec-delete',      'part of NDN security tools', None, 1),
+    ('manpages/ndnsec',              'ndnsec',              'NDN security toolkit', None, 1),
+    ('manpages/ndnsec-cert-dump',    'ndnsec-cert-dump',    'export an NDN certificate', None, 1),
+    ('manpages/ndnsec-cert-gen',     'ndnsec-cert-gen',     'create an NDN certificate for an identity', None, 1),
+    ('manpages/ndnsec-cert-install', 'ndnsec-cert-install', 'import an NDN certificate from a file', None, 1),
+    ('manpages/ndnsec-delete',       'ndnsec-delete',       'delete an NDN identity, key, or certificate', None, 1),
     ('manpages/ndnsec-export',       'ndnsec-export',
-     'export a certificate and its private key to a file', None, 1),
-    ('manpages/ndnsec-get-default',  'ndnsec-get-default', 'part of NDN security tools', None, 1),
+     'export an NDN certificate and its private key to a file', None, 1),
+    ('manpages/ndnsec-get-default',  'ndnsec-get-default',
+     'show the default NDN identity, key, and certificate for the current user', None, 1),
     ('manpages/ndnsec-import',       'ndnsec-import',
-     'import a certificate and its private key from a file', None, 1),
-    ('manpages/ndnsec-key-gen',      'ndnsec-key-gen',     'part of NDN security tools', None, 1),
-    ('manpages/ndnsec-list',         'ndnsec-list',        'part of NDN security tools', None, 1),
-    ('manpages/ndnsec-set-default',  'ndnsec-set-default', 'part of NDN security tools', None, 1),
-    ('manpages/ndnsec-sign-req',     'ndnsec-sign-req',    'part of NDN security tools', None, 1),
-    ('manpages/ndnsec-unlock-tpm',   'ndnsec-unlock-tpm',  'part of NDN security tools', None, 1),
-    ('manpages/ndn-client.conf',     'ndn-client.conf',    'Configuration file for NDN platform', None, 5),
-    ('manpages/ndn-log',             'ndn-log',            'ndn-cxx logging',                     None, 7),
+     'import an NDN certificate and its private key from a file', None, 1),
+    ('manpages/ndnsec-key-gen',      'ndnsec-key-gen',
+     'generate an NDN key for an identity', None, 1),
+    ('manpages/ndnsec-list',         'ndnsec-list',
+     'list all known NDN identities, keys, and certificates', None, 1),
+    ('manpages/ndnsec-set-default',  'ndnsec-set-default',
+     'change the default NDN identity, key, or certificate for the current user', None, 1),
+    ('manpages/ndnsec-sign-req',     'ndnsec-sign-req',     'generate an NDN certificate signing request', None, 1),
+    ('manpages/ndnsec-unlock-tpm',   'ndnsec-unlock-tpm',   'unlock the TPM', None, 1),
+    ('manpages/ndn-client.conf',     'ndn-client.conf',     'configuration file for NDN platform', None, 5),
+    ('manpages/ndn-log',             'ndn-log',             'ndn-cxx logging',                     None, 7),
 ]