New style for shared links. Preparation for changes in some addons

This is the foundation for changes I made with the connectors that import articles from facebook, twitter and G+. They are now using the [class] bbcode to do a nicer formatting of shared links.

In bbcode.php I had to add additional characters to be able to have a class name with a "-" in it.

Concerning the fetching of information from a web page I found out that oembed on some pages gives more information than the other methods. So parse_url now fetches his information from oembed as well.

In "vier" I did the changes I described above, Additionally I moved the notifications a little bit down - so that they don't hide the menu anymore. Additionally i corrected a problem that the cursor hadn't the right shape on some icons.