Support for await

[FlowIT-JIT]

Async. operations such as HTTP Requests should return a thenable or promise to support await and .then(..).

A good article on the subject can be found here:
https://developers.google.com/web/fundamentals/primers/promises

Quick and dirty example of the concept of thenables which would be cross browser compatible - the use of promises would not: https://caniuse.com/#feat=promises

async function getData()
{
	var callbacks = { resolve: undefined, reject: undefined };
	var promise = { then: function(resolve, reject) { callbacks.resolve = resolve; callbacks.reject = reject; } };

	setTimeout(function() { callbacks.resolve("Hello world"); }, 2000);
	
	return promise;
}

// Test using .then(..)
getData().then(function(res) { console.log("Thenable result: ", res); });

// Test using await
var result = await getData();
console.log("Awaited result: ", result);

[FlowIT-JIT]

https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/await
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/async_function
https://javascript.info/async-await
https://javascript.info/promise-chaining
https://developers.google.com/web/fundamentals/primers/promises
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise
https://www.promisejs.org/implementing/
https://github.com/jquery/jquery/blob/master/src/deferred.js
http://api.jquery.com/category/deferred-object/
https://api.jquery.com/deferred.promise/

[FlowIT-JIT]

Closed as this was obviously a bad idea since we cannot mark functions as async since IE does not support this. So functionality within Fit.UI should not be async and return promises by default.
However, having some sort of Promise/Thenable object that is compatible with the native implementation might make sense at some point.