Add show in app and delete links in resource level pages

[vala]

When available, we'd like to automatically generate a "Show in app" link for :crud and :form resources, and add it to crud table actions and edit forms.

Also, displaying a "Delete" button at the resource level (edit forms) seems to be useful after some end user feedbacks.

• crud/index "Show" table action
• crud/edit "Show" and "Delete" button actions
• form/edit "Show" and "Delete" button actions