refs #17 'rails generate model category name type' and 'rails generate migration AddProjectIdToCategories project_id:integer'
refs #110 delete controller methods
refs #17 'rails generate migration AddDeletedAtToCategories deleted_at:timestamp'
refs #17 change ticket_category -> category
refs #17 'rails generate model categorization registrable_id:integer registrable_type category_id:integer'
refs #17 add polymorphic to the categorizations, and add relationship of categories, tickets and blogs