- Directive `mw-listable-action` was added to define a custom action that is registered as action column similiar
to `mw-list-url-action-button` only that you can transclude custom content and define custom function.
Custom function is executed on click of the element and when the user double clicks on the row.
```html
<td mw-listable-action="action()">
<div mw-arrow-button></div> <!-- transclude custom content -->
</td>
```
- Colspan of action column header is now set correctly. It uses the maximum of registered `mw-listable-action` per row.
So when the first row registers only one `mw-listable-action` but the second registers two the colspan of the
action column header element will be set to two
