Update models.py
Update models.py

Add description and read_only to motion/number_value.

ostcar/OpenSlides,normanjaeckel/OpenSlides,ostcar/OpenSlides,tsiegleauq/OpenSlides,OpenSlides/OpenSlides,ostcar/OpenSlides,normanjaeckel/OpenSlides,tsiegleauq/OpenSlides,normanjaeckel/OpenSlides,tsiegleauq/OpenSlides,OpenSlides/OpenSlides,normanjaeckel/OpenSlides