Rename AttachmentsController to CmaCaseAttachmentsController
Rename AaibReportsAttachmentsController to be singular

This is the correct rails best practices
Rename ManualDocumentsAttachments to be singular

This is the rails best practices for controller naming conventions
Create and use AbstractAttachmentsController

This commit provides setup for making use of an abstract attachment controller which will provide common functionality to CmaCase and AaibReport attachments controllers
CmaCaseAttachment services to their own registry

In order to clean up the code and require different sets of services per controller, move the CmaCase related Attachment sevices to their own registry. We can now use a services method in the controller to decide which service registry to use
Correct spelling of registry
Move services method into attachment controller
Refactor servies to implement the same api
Abstract common attachment controller code

The only thing that is now not common in the controller code is the redirect path. Once we move this into a 'redirect_path' helper we can use the same code across the board for all attachments
Use private instead of protected

See Dom's comments here:
https://github.com/alphagov/specialist-publisher/pull/181#discussion_r15332303
Rename attachment_services to services
Rename redirect_path to edit_path
Get repository dependency from wiring directly
Create AbstractAttachmentServiceRegistry
Refactor object type out of service method names

We are already dealing with the AttachmentServiceRegistry so we don't need to call 'new_attachment'. Instead just use 'new'
Merge pull request #181 from alphagov/refactor/dry-up-attachments-controller

Dry up Attachments controllers
Importer set up initially to import AAIB reports

From `import/metadata` (json files, see spec/fixtures/import) and
`import/downloads`, import AAIB reports.

Also create an optional decorator used to validate that all attachments
for a document have been referenced in the body of that document.

Worked on by myself and @bestie
Handle duplicate titles.

 * For documents which already have a newer version, just skip it.
 * For documents which have an older version, delete that version and
   import the newer instead.
String body substitutions (PDF image) on AAIB reports
Import all the AAIBS