brewnit: Grammar update for units

Signed-off-by: Lucas Bajolet <lucas.bajolet@gmail.com>
brewnit: Moved model entities to model folder

Signed-off-by: Lucas Bajolet <lucas.bajolet@gmail.com>
brewnit: Update generated parser

Signed-off-by: Lucas Bajolet <lucas.bajolet@gmail.com>