Recycler standby

[helfer]

This PR introduces a new fetch policy, which can be used by react-apollo and other integrations to keep a query in Apollo's store, but mark it as "standby". Standby queries will not watch the store, will not be refetched on store reset, but can be used in updateQueries and refetchQueries calls. This is mainly a response to issues like apollographql/react-apollo#622 and apollographql/react-apollo#531.

• Make sure all of the significant new logic is covered by tests
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• Update CHANGELOG.md with your change
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• If this was a change that affects the external API, update the docs and post a link to the PR in the discussion