Redesign Entityreference Browser

I think we also should redesign the browser. And adding an entity to the browser via javascript is not cool. So I think first we should use a table, so you can use tablesort later. And the inserting stuff should happens via ajax. I started with rebuildung the browser. Later I will work on the ajax stuff and the ctools object cache which should we use to store the selected entities.

You can find my last patch here.