Images endpoint

[scotchneat]

Adding the /images endpoint/routes.

Opening this PR now as a draft since it's a work in progress.

This PR includes the following methods:

• - List all images: GET /images
• - Retrieve an image by id or slug: GET /images/{image_identifier}:
  • List All Distribution Images: type=distribution query param
  • List All Application Images: type=application query param
  • List a User's Images: private=true query param
  • List Images by Tag: tag_name=XXXX query param
• Retrieve an Existing Image by ID or slug
• Create a Custom Image
• Update an Image
• List All Actions for an Image
• Delete an Image

[hilary]

It's unfortunate that you can't reuse the images model... We may want to mark the readOnly fields that way anyway...

[scotchneat]

I'm going to cancel this PR and break it up to smaller chunks. This will allow me to also start the Actions Endpoint to have the dependent pieces done before doing the Images Actions endpoints.