Shorter links for ModelAdmin items

[sminnee]

Right now an item on a ModelAdmin has the URL of: /admin/(modeladmin)/(tab)/EditForm/field/(tab)/item/214/edit

This would be usefully contracted to without losing ambiguity: /admin/(modeladmin)/(tab)/edit/214

• $Tab/edit/$ID Can be a new rule.
• The default action (edit) can be supplied by the rule (since edit precedes the ID)

Changing the URLs in this way could be disruptive and so I would introduce it as an optionally enabled feature of ModelAdmin in 4.x.

To implement this, will require:

• A new routing rule on ModelAdmin
• A mechanism for monkeypatching the GridField item request URL generation. Probably a setter method on the GridFieldConfig component that lets the Base URL be overridden.