Add examples of using @Install handlers

[knstvk]

Environment

• Documentation version: 7.2
• Part of the documentation: Manual
• Existing page: https://doc.cuba-platform.com/manual-7.1/gui_LookupField.html and similar

Description of the bug or enhancement

For methods like setOptionImageProvider() (i.e. setters of providers) add examples of using them with @Install (by generating this code in Studio "Handlers" tab):

@Inject
private Image imageResource;

@Install(to = "fooLookupField", subject = "optionImageProvider")
private Resource fooLookupFieldOptionImageProvider(Foo foo) {
    String iconName = Boolean.TRUE.equals(foo.getStatus()) ? "icons/active.svg" : "icons/inactive.svg";
    return imageResource.createResource(ThemeResource.class).setPath(iconName);
}

[knstvk]

Duplicate of #474