Add ComboBox and TextField "emptyText" (==InputPrompt) attribute serverside (client basic impl exists)

[Marc Englund]

(NOTE at least textfield could use the same functionality; implement or create eparate ticket.)

Client basic functionality done (weekend coding), but should add CLASSNAME_EMPTY as well, as indicated by TODOs.

Server impl here:

    public String getEmptyText() {
        return emptyText;
    }

    public void setEmptyText(String emptyText) {
        this.emptyText = emptyText;
    }

    public void paintContent(PaintTarget target) throws PaintException {
        if (emptyText != null) {
            target.addAttribute("emptytext", emptyText);
        }
        super.paintContent(target);
    }

Test! ComboBox? has many modes!

(Implemented during weekend, decided against committing during bug-fix sprint.)

[Marc Englund]

NOTE this feature is based on a real user need.

[Marc Englund]

Rename emptyText -> Input Prompt http://designinginterfaces.com/Input_Prompt

(requested in forum)