ament_pep257 does not match pydocstyle's pep257 definition

[Arnatious]

The set of ignores that defines pep257 in pydocstyle http://www.pydocstyle.org/en/latest/error_codes.html#default-conventions

['D203', 'D212', 'D213', 'D214', 'D215', 'D404', 'D405', 'D406', 'D407', 'D408', 'D409', 'D410', 'D411', 'D413', 'D415', 'D416', 'D417']

versus the set of default ignores in ament_pep257

['D100', 'D101', 'D102', 'D103', 'D104', 'D105', 'D106', 'D107', 'D203', 'D212', 'D404']

Results in the following checks that are not part of pep257 being run

['D213', 'D214', 'D215', 'D405', 'D406', 'D407', 'D408', 'D409', 'D410', 'D411', 'D413', 'D415', 'D416', 'D417']

pydocstyle generates the list of codes to check by either using a convention or an ignore list. ament_pep257 currently uses --ignore

ament_lint/ament_pep257/ament_pep257/main.py

Line 120 in db91e6c

'--ignore=' + ','.join(ignore),

This should probably be changed to --add-ignore. Then, pydocstyle will default to using --convention=pep257, and then pep257's defaults are used in addition to any user specified ignores.

We can simplify the default ignores at that point to just ['D1']

ament_lint/ament_pep257/ament_pep257/main.py

Lines 48 to 51 in db91e6c

	default=[
	'D100', 'D101', 'D102', 'D103', 'D104', 'D105', 'D106', 'D107',
	'D203', 'D212', 'D404',
	],