Handle wildcard imports: import * as something from '@ember/something'

https://github.com/babel/ember-cli-babel/issues/170#issue-246272427

> The [`import` statement](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/import) supports importing all named exports into an object.
>
>For example, instead of this
>
>```js
>import {
> alias as computedAlias,
> and as computedAnd,
> // ...
>} from '@ember/object/computed';
>import { decoratedPropertyWithRequiredParams } from '../utils/decorator-macros';
>
>export const alias = decoratedPropertyWithRequiredParams(computedAlias);
>```
>
> you could just do this
>
> ```js
> import * as computed from '@ember/object/computed';
> import { decoratedPropertyWithRequiredParams } from '../utils/decorator-macros';
>
> export const alias = decoratedPropertyWithRequiredParams(computed.alias);
> ```
>
> But apparently, the latter does not work. :slightly_frowning_face:
>
> ```
> Could not find module `@ember/object/computed` imported from `ember-decorators/object/computed`
> ```

https://github.com/babel/ember-cli-babel/issues/170#issuecomment-318635180
> We would need to handle wildcard import in babel-plugin-ember-modules-API-polyfill. This seems reasonable to me though. We would need to check if the specified module contains only exports from a single namespace or multiple. If multiple namespaces we would have to build up the intermediate POJO that would be used.