Infinite scroll, "new share" is now standard

This pull request contains especially two new things - and some bugfixes and enhancements

* Infinite scroll can be activated (is deactivated by default and has still some issues)
* Instead of activating "new share" this is now activated by default and can be deactivated

Small enhancements:
* There is a separate configuration setting that imported reshared postings look like "wall to wall" posts.
* Searching for tags should be much faster now.
* when repeating items that will be send to text based networks the repeat string now includes the name as well.

Bugfix:
* Preview sometimes didn't work because our user agent was blocked - so its now a different one
* Link detection (that is used for exporting to other networks) had a bug that sometimes link weren't detected