Most Toaster tables include a controls area right above the content with a set of common controls: a search form, an 'edit columns' menu and a 'show rows' dropdown.

Some of those tables, however, require additional actions. For example:

* the all layers table (http://www.yoctoproject.org/toaster/all-layers.html)
* the custom image recipes table 
* the add / remove packages table we will use to customise the package content of custom image recipes

We need to be able to add those actions.