Improve default resource display

Created by: gracewashere

Closes #129 (closed)

Problem:

Administrate relies on #to_s to display resources throughout the system. In order to get Administrate working correctly, developers must define #to_s on all models that will be displayed in the admin dashboard.

This process is not documented, can be confusing, and gets in the way of a zero-configuration dashboard.

Solution:

Add Administrate::BaseDashboard#display_resource, which takes a resource and returns a sensible string representation. Devs can overwrite this method on a per-dashboard basis to customize how their resources are displayed.

In order to document this method, we generate comments in each dashboard class that follow the format:

  # Overwrite this method to customize how line items are displayed
  # across all pages of the admin dashboard.
  #
  # def display_resource(line_item)
  #   "LineItem ##{line_item.id}"
  # end

TODO

• Add comments to generated dashboards
• CHANGELOG