Bugfix: Connecting with other users works again/Some more profile optimizing

The last pull request contained a bug so that you couldn't add other contacts. This is now solved.

Some more stuff:
* If a post is a pure reshare (mostly diaspora postings) then the "display" page shows the profile of the reshared user.
* oembed had the problem that sometimes it returned an empty link description.
* The bbcode conversation for attachments had problems with "[" and "]" in the link description.
* When searching for displayable posts on the "display" page, now the "hidewall" status is respected