Allow property based dependency specification in ng_di

As discussed in #138, ng_di currently doesn't allow property based dependency specifications like:

``` javascript
class MyController {

static get $inject() {
return ['DataStore'];
}

constructor(DataStore) {
this.dataStore = DataStore;
}

toggle() {
this.active = !this.active;
this.dataStore.addData('active', this.active);
}
}
```

Proposal: add possibility to configure `'ng_di': [2, 'property']`