Graphql Core Documentation (#59)

* Added help and about for GraphQL service

* fix broken tests and urls in readme

* Update GraphQL URL and queries/responses

* update URL

* remove host from URL

* Update using-graphql.md

* Apply suggestions from code review

Co-authored-by: Ben Moore - Ensembl <bmoore@ebi.ac.uk>

* Removed status and tags

* implement suggested changes in the PR

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Co-authored-by: Beth Flint <beth@ebi.ac.uk>
Co-authored-by: bethflint <45971031+bethflint@users.noreply.github.com>
Co-authored-by: Ben Moore - Ensembl <bmoore@ebi.ac.uk>