Add integration with GraphQL

[c-w]

This pull request adds a connection and data-source for GraphQL.

To test the integration, place the following content into a file called graphql.private.js in the server/dashboards folder:

return {
  id: "graphql",
  name: "GraphQL",
  icon: "dashboard",
  url: "graphql",
  description: "A basic sample to see how a GraphQL service is connected to graphs",
  preview: "/images/bot-framework-preview.png",
  config: {
    connections: {
      graphql: { serviceUrl: "https://pokeapi-graphiql.herokuapp.com" }
    },
    layout: {
      isDraggable: true,
      isResizable: true,
      rowHeight: 30,
      verticalCompact: false,
      cols: { lg: 12, md: 10, sm: 6, xs: 4, xxs: 2 },
      breakpoints: { lg: 1200, md: 996, sm: 768, xs: 480, xxs: 0 }
    }
  },
  dataSources: [
    {
      id: "pokeIds",
      type: "Constant",
      params: { values: [12, 13, 14], selectedValue: 12 },
      calculated: (state, dependencies) => {
        return { variables: { pokeId: state.selectedValue } };
      }
    },
    {
      id: "graphql",
      type: "GraphQL",
      dependencies: { variables: "pokeIds:variables" },
      params: { 
        query: "query($pokeId:Int!){pokemon(number:$pokeId){name}}"
      },
      calculated: (state, dependencies) => {
        return { pokemons: [state.data.pokemon] };
      }
    }
  ],
  filters: [
    {
      type: "TextFilter",
      title: "PokeId",
      dependencies: { selectedValue: "pokeIds", values: "pokeIds:values" },
      actions: { onChange: "pokeIds:updateSelectedValue" },
      first: true
    },
  ],
  elements: [
    {
      id: "names",
      type: "Table",
      size: { w: 4, h: 8 },
      dependencies: {
        values: "graphql:pokemons"
      },
      props: {
        cols: [
          { header: "Name", field: "name" }
        ]
      },
    }
  ],
  dialogs: []
}

Open the thus-defined dashboard to fetch the name for a Pokemon from the GraphQL PokeAPI and display it in an Ibex table:

[morsh]

@c-w not sure if this should be approved prior event hub. Plus, add this sample (minus the connection string) to the dashboard samples once you added event hub integration and add html instructions how to add the connection string (under connection => editor)

[morsh]

@c-w - very small comments. Great work!
Please get the latest changes and solve the conflicts, if there are any.

[morsh]

const params = this.getParams() || {};
const { query } = params || {};

[c-w]

The suggested code doesn't compile, but I managed to add default values in 4dcbd0e.

[morsh]

I find that using lodash is more readable, especially if you have it in your project. But that is just a recommendation, not a must. Plus, you can use a simpler form of assign to property:

Object.assign(dependencies, { selectedValues });

[c-w]

This is copied from other updateSelectedValues implementations (e.g. Sample.ts, Azure.ts) so I'd say that we should clean this up in bulk in the future.