Updating generator to stub Catalog

Instead of deleting the CatalogController, I want the generatore (i.e.
`rails g curate`) to create a app/controllers/catalog_controller.rb
that requires Curate's catalog controller. It can then be overriden
as required.

Closes ndlib/planning#88
Addresses curationexperts/curate_dce#2
Merge pull request #56 from ndlib/planning-88-search-results

Updating generator to stub Catalog