Compiler throws when using namespace import on engine

[pmdartus]

Description

When transforming a namespace import on engine the compiler throws. For example:

import * as engine from 'engine';
export default class Test extends engine.Element {}

Error:

Cannot read property 'name' of undefined.

While we need to fix the uncaught exception, this bug opened another discussion concerning if we should or not allow namespace import on engine. While the following code is valid javascript, it will be hard for the compiler to transform the decorator.

import * as engine from 'engine';
export default class Test extends engine.Element {
      @engine.api props;
}

It appears that we want to block namespaced import for now. We can still relax it in the future if requested.

[caridy]

I'm fine with this for now since we eventually will remove engine, and use a more formal name.