Removed TODO placeholders in commands description

It's better than nothing but not by that much

export.py

@@ -9,31 +9,36 @@ if __name__ == '__main__':
 
     # Parsing arguments
     parser = argparse.ArgumentParser(
-        description="TODO")
+        description="Export the hostnames rules stored "
+        "in the Database as plain text")
     parser.add_argument(
         '-o', '--output', type=argparse.FileType('w'), default=sys.stdout,
-        help="TODO")
+        help="Output file, one rule per line")
     parser.add_argument(
         '-f', '--first-party', action='store_true',
-        help="TODO")
+        help="Only output rules issued from first-party sources")
     parser.add_argument(
         '-e', '--end-chain', action='store_true',
-        help="TODO")
+        help="Only output rules that are not referenced by any other")
     parser.add_argument(
         '-r', '--rules', action='store_true',
-        help="TODO")
+        help="Output all kinds of rules, not just hostnames")
     parser.add_argument(
         '-b', '--base-rules', action='store_true',
-        help="TODO implies rules")
+        help="Output base rules "
+        "(the ones added by ./feed_rules.py) "
+        "(implies --rules)")
     parser.add_argument(
         '-d', '--no-dupplicates', action='store_true',
-        help="TODO")
+        help="Do not output rules that already match a zone/network rule "
+        "(e.g. dummy.example.com when there's a zone example.com rule)")
     parser.add_argument(
         '-x', '--explain', action='store_true',
-        help="TODO")
+        help="Show the chain of rules leading to one "
+        "(and the number of references they have)")
     parser.add_argument(
         '-c', '--count', action='store_true',
-        help="TODO")
+        help="Show the number of rules per type instead of listing them")
     args = parser.parse_args()
 
     DB = database.Database()