Service feedback: switch from support to support-api
Use module accessors to store the API clients

This reduces duplication a little bit
Enable/disable support-api with a feature flag

This is a very temporary step so that `feedback` app deploys aren't
blocked by needing to have the `support-api` running smoothly in production.
Merge pull request #132 from alphagov/switch-service-feedback-to-support-api

Switch service feedback to 'support-api'