Fixed leftover
Update all views when changing showAll

We cannot update all views at once, because this happens:
```
file:///usr/share/harbour-ttrss-cnlpete/qml/models/FeedModel.qml:51:
TypeError: Cannot read property 'categoryId' of null
```

Tested on sailfish
Closes #142
[sailfish] Cleaned up (DRY)
Merge branch 'fixShowAll' of git://github.com/michael-k/ttrss into michael-k-fixShowAll
only redisplay categories with showall flag on updateView(), regards #142