title: Firestore console changes does not trigger snapshotChanges subscription
body: <p>I am trying to subscribe to a document in Firestore by using AngularFire. When I edit my document through Firestore console, I cannot see any difference in the pulled data even after refreshing my local. DocumentChangeAction.type is still "added" after modification.</p>
  
  <p>Doesn't console changes suppose to trigger "modified" action even for manual updates ?</p>
  
  <p>Thanks.</p>
  
  <pre><code>retrieveUserPosts666 (uid: string, page, lastKey,now:number, nowBefore30:number) {
  
          let plizt = [];
  
          return this.afs.collection&lt;any&gt;("uk", ref =&gt; {
  
              let query : firebase.firestore.CollectionReference | firebase.firestore.Query = ref;
  
              query = query.where('uid','==',uid);
              query = query.orderBy('postdate','desc');
              query = query.startAt(lastKey).limit(page);
  
              return query;
  
          }).snapshotChanges().map(x=&gt; {
  
              x.forEach((post, index) =&gt; {
  
                  plizt.push({
                      "key": post.payload.doc.id,
                      "itm": post.payload.doc.data(),
                      "city" : this.retrieveBeatifulCityName(post.payload.doc.get('city')),
                      "cut_en" : post.payload.doc.get('description_en').substring(0,100) + "..."
                  })
  
              });
              return plizt;
          })
  
      }
  </code></pre>