When assets have been copied with rake admin:copy_assets, then rails_admin should NOT insert
another ActionDispatch::Static middleware, because it eclipses Rails's native middleware and assets
are loaded from rails_admin's public folder instead of the application's public folder.
Fixed by checking if any of the rails_admin subdirectories exist in any of the static asset classes
Also, if the middleware is inserted, it should be done AFTER, not IN FRONT of Rails's own static asset
middleware, to permit precedence to the application's public folder over the gem's.
The model label is now configurable at the model level only, and is no longer configurable
at the section level (list, navigate, update,...), as this was considered overkill.
This refactoring was in part motivated by issue #319 which reported that display of labels was very inconsistent across
various screens, and the label configuration, if given, was not consistently effective.
The Labelable module was removed, and the methods model into config/model.rb
All references to label across the code have been updated to use the model configuration.
Specs updated and passing. Readme also updated accordingly.