Add additional inputs for BusinessSupportEditions

Adds priority, start and end date and facet inputs for BusinessSupportEdition.
govuk_content_models https://github.com/alphagov/govuk_content_models/commit/5bae378b017a45ad49d15f31b28c2da152d67db4
necessary for this to work so no version bump to content models gem in this commit.
Add seed and migration for facet values
Add imminence facet data importer and task
Add migration to call the facet data import task
Use seed data in facet values migration

The seed data was duplicated in the migration. Sub-optimal for the obvious reasons.
Loads the seed file in the migration so the datas live in once place.
Disable facet fields for published editions
Ensure all fields are disabled for published editions

Additionally, when all facets are selected, make sure the 'all' check box is checked.
Ordering business support finder facets alphabetically for easier scanning, with help from @steventux. Some basic layout tweaks to improve layout
Further layout tweaks. Added .facing class to allow us to put blocks of checkboxes in facing columns. Easier to scan
I need to use ids for more granular styling. They had spaces in them, so swapped for underscores
Opted to style facing columns of checkboxes using ids instead, faster, easier. Removed redundant .facing class
Added heading to start and end date selection to make it easier to scan
Simplified the ids and labels using the model_collection
Making font weights consistent in the UI