Added BackLayout, Year model classes.

Signed-off-by: Kouhei Maeda <mkouhei@palmtb.net>
Changed to ignore pep8 violations about generated migration code.

Signed-off-by: Kouhei Maeda <mkouhei@palmtb.net>
Changed executing pylint in pre-commit hoook.

Signed-off-by: Kouhei Maeda <mkouhei@palmtb.net>