Add WP CLI scripting for the replacement of old image URLs

Before merging, it would be cool if this new WP CLI command did this for us:

* [x] List images by domain and path
* [x] Has a better command name than `newsfix`
* [x] Sideload images into WordPress
* [x] Ensure we track the sanitization of the new file into a useable URL
* [x] Replace instances of sideloaded image with new URL
* [x] Attach images that are used once to their parent post

`wp image-fix list` currently works to display image domain and path statistics in post content.
`wp image-fix sideload http://news.wsu.edu` currently works to sideload images into WordPress