Migration to fic business_support facet duplication

When the data was imported, some of the slugs in the schemes were added
multiple times.  This was causing noide in the CSV report.
Remove code to migrate facets to stored slugs

It's been run on prod, so it now redundant.
Remove relationships between facets and schemes

These are redundant as we're now storing an array of facet slugs on the scheme instead.
Merge pull request #38 from alphagov/fix_business_support_facet_duplication

Fix business support facet duplication