Transform issue page into a stream

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 #1 to be merged first and a rebase onto master after that. Something along the lines of:

```
$ git rebase --onto master 8c3ed4097194019faf3487f7ff69dd7141fd7222
```