[HPT-79] Limit discovery by type

Fulfills https://bugs.dlib.indiana.edu/browse/HPT-79

This pull request adds/changes:

app/controllers/catalog_controller.rb
- Adds behaviors and options for the type attribute
- Configures the type attribute to be included in facet controls

 app/controllers/pageds_controller.rb
- Allows processing of type as a parameter

app/models/paged.rb
- Adds type to the model

app/views/pageds/*
- Adds type to views, partials, etc.

spec/controllers/catalog_controller_spec.rb
- Adds faceted search tests for the type attribute with new factories

spec/models/paged_spec.rb
- Refactor of paged model tests to use Factory Girl to fix https://bugs.dlib.indiana.edu/browse/HPT-150