Fix generation of second/subsequent resources in an extension

[anitagraham]

This PR changes the order of frontend routes generated when adding a second or subsequent route to an extension. See gitter discussion with jussihirvi on May 10.

The current routes generated by

generate refinery:engine place name:string
generate refinery:engine person  name:string --extension places --namespace places

are (with intervening lines removed)

  # Frontend routes
  namespace :places do
    resources :places, :path => '', :only => [:index, :show]
  end
  # Frontend routes
  namespace :places do
    resources :people, :only => [:index, :show]
  end

Trying to access /places/people results in "Couldn't find Refinery::Places::Place with 'id'=people", as routes are matched in the order defined.

With the changes the routes (with even more lines removed) become:

  namespace :places do
    resources :people, :only => [:index, :show]
    resources :places, :path => '', :only => [:index, :show]
  end