10 add support for ampe token to batching server

[b-yap]

closes #10 .

General overview of the changes:

1. Edit the schema.graphql to make it parse-able for the lib graphql-client
2. Added the query as provided by @ebma (ampe_query.graphql) :

    query MyQuery {
        bundleById(id: "1") {
           ethPrice
        }
    }

3. Following graph-ql-client's example, introduced AmpePriceView struct.