Can't use more 'items' sections

[lukaszachy]

When two 'items' type sections are used, did ends up with traceback. It looks as did is trying to register first section again.

Command did --config items

Traceback (most recent call last):
  File "/usr/local/bin/did", line 42, in <module>
    did.cli.main()
  File "/usr/local/lib/python3.7/site-packages/did/cli.py", line 188, in main
    options, header = Options(arguments).parse()
  File "/usr/local/lib/python3.7/site-packages/did/cli.py", line 62, in __init__
    self.sample_stats.add_option(self.parser)
  File "/usr/local/lib/python3.7/site-packages/did/stats.py", line 225, in add_option
    stat.add_option(parser)
  File "/usr/local/lib/python3.7/site-packages/did/stats.py", line 149, in add_option
    stat.add_option(group)
  File "/usr/local/lib/python3.7/site-packages/did/stats.py", line 55, in add_option
    "--{0}".format(self.option), action="store_true", help=self.name)
  File "/usr/lib64/python3.7/argparse.py", line 1373, in add_argument
    return self._add_action(action)
  File "/usr/lib64/python3.7/argparse.py", line 1577, in _add_action
    action = super(_ArgumentGroup, self)._add_action(action)
  File "/usr/lib64/python3.7/argparse.py", line 1387, in _add_action
    self._check_conflict(action)
  File "/usr/lib64/python3.7/argparse.py", line 1526, in _check_conflict
    conflict_handler(action, confl_optionals)
  File "/usr/lib64/python3.7/argparse.py", line 1535, in _handle_conflict_error
    raise ArgumentError(action, message % conflict_string)
argparse.ArgumentError: argument --foo: conflicting option string: --foo

Configuration file items

[foo]
type = items
header = Work on this
item1 = foo - A
item2 = foo -A

[bar]
type = items
header = Work on that
item1 = foo - A
item2 = foo -A

[psss]

Seems we have to handle items type as a special case because the options are gathered under a single option group. In the future we could consider creating a separate group for each if it makes sense. For now I just made it working the old way with the new plugin detection.

[psss]

Example output with your config:

* Work on this
    * foo - A
    * foo -A

* Work on that
    * foo - A
    * foo -A

Help message looks fine as well:

Custom stats:
  --foo            Work on this
  --bar            Work on that
  --custom         All above