Nested collection links should honour routes

Created by: karlentwistle

Prior to this commit if any routes where omitted for a resource like:

resources :users
resources :orders, except: [:edit, :update]

Navigating directly to a orders show page would correctly omit the edit link but if another associated dashboard utilised a field that rendered using the partial _collection.html.erb like:

class UserDashboard < Administrate::BaseDashboard
  ATTRIBUTE_TYPES = {
    orders: Field::HasMany,
  }

  SHOW_PAGE_ATTRIBUTES = ATTRIBUTE_TYPES.keys
end

when navigating to the users show page an error 500 would be thrown because the rendering of orders would incorrectly try to link to the non existent edit route

Fixes #790 (closed)