Provide `.promise()` functions to the old endpoint along with promise-polyfilled library

[mktange]

Similar to XrmQuery for the Web API, the old endpoint should also have .promise() functions next to their .execute() functions, which returns a ES6 Promise instead of relying on callbacks.

A new JavaScript library file should also be generated which includes a promise polyfill (dg.xrmquery.rest.promise.min.js), just like it is for the Web API version.