Transform issue page into a stream #3

Display municipality updates and issue comments in a stream on a single page.

This branch is based on 'sidonath:municipal-admin-updates' so it needs #4 to be merged first and a rebase onto master after that. Something along the lines of:

```
$ git rebase --onto master 8aaeac6e69458dcfbda565c2a7e6c2fd5879fd29
```