app.net feeds, number of comments and better handling of the reply button in "vier"

Just some more minor stuff.

-When you click on the "reply" button, then now the focus is set to this textarea. That means that people can click on the button and can start to type the comment.
- app.net exports a users timeline as an RSS feed. There are some improvements now to make them look better in friendica. There is still work to be done, but this should be good improvement.
- There already was a setting for the maximum number of comments per post. This setting is now reachable via the admin interface.