Created by: KjellMorgenstern
This pull request adds a button for creating new items underneath each "has_many" field. Example: class order has many line_items. In the GET admin/orders/1 view, the line_items are listed. Now, after that list, a "New line_item" button is added. When clicked, it leads to GET admin/orders/1/line_items#new , and the line_item form has order#1 preselected in the order_id field.
I use this by default for each model. Maybe others find it useful, so here is a generic version of it. I think the layout could use some polishing (using 'div' is probably not in line with adminstrate), but first I'd like to collect some feedback.