[Wicket Viewer] Support for Actions in Collection View

The programming model is already sufficient to cover this use-case:

If an action is NOT hiddenWhere in tables, then show it in tables.

Design Proposal:

The last column in tables named `Actions` shall be dedicated to actions.

Scenarios within a single table cell:

• If only a single action is shown, then render it as a button.
• If less than configurable threshold of actions is shown, render them as buttons in a vertical layout (because, that aligns with how we allow for cell to render plurals/collections)
• If more than configurable threshold of actions is shown, then collect them into a dropdown menu (with ellipsis). ... perhaps could however render a primary action as button still