Add oae:id to the activity view item model in the activity adapter, Fix changepicutre dialog not opening second time

When uploading a new profile picture the UI should be updated everywhere the old picture was displayed. Currently there is a regression where the activity actor picture isn't updated after uploading the picture. In the screenshot you'll see that general ackbar is still set as my profile picture and hasn't been updated to a selfie.

![screen shot 2014-06-17 at 16 25 38](https://cloud.githubusercontent.com/assets/218391/3302368/ba9242fc-f633-11e3-9b12-468fe192a42a.png)

In the activitystrea.ms model, the `id` is a globally unique URI to the item (i.e., a full URL). That's why we have the OAE extension parameter `oae:id` which represents just the OAE-unique id.