Fix named-amd exports.

Ember does not export named-amd yet. We are shimming the `ember` module to have a single `default` export (this is exactly what EAK and ember-cli expect).

This means that using the following:

```javascript
import {get} from 'ember';
```

Which transpiles to:

```javascript
var get = __dependency1__.get;
```

Will not actually work since `__dependency1__` will only have a single property (`default`) and not a `get` property.

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This changes the imports to match reality. At some point, Ember will actually provide real ES6 (and possibly AMD) builds so I kept the variables that we were importing previously stashed at the top of each module (so that when we can do `import {get} from 'ember';` it is as simple as changing these same lines back).
We need to restructure the internal modules to be in a much saner layout.  Once we release an officially supported ES6 build, we are immediately locked into supporting that API (due to SemVer) so when we release it we MUST be fully satisfied with that module layout.