Enable multiple schema

[mcg-web]

Multiple schema endpoint

#app/config/config.yml

overblog_graphql:
    definitions:
        schema:
            foo:
                query: fooQuery
            bar:
                query: barQuery
                mutation: barMutation

foo schema endpoint can be access:

type	Path
simple request	/graphql/foo
batch request	/graphql/foo/batch
graphiQL	/graphiql/foo

bar schema endpoint can be access:

type	Path
simple request	/graphql/bar
batch request	/graphql/bar/batch
graphiQL	/graphiql/bar