refs https://github.com/TryGhost/Team/issues/1037
Tiers have a new `type` column to differentiate between `free` and `paid` tiers. This change -
- sets type as paid for all new tiers created, as `free` tier is created by default
- excludes any price/stripe data change for free tier
- updates all usages of default product to fetch the first paid product from the products list in DB instead of just the first product it finds.
ca18f140c4