One of the goals is to make the generated content directory directly hostable
via a web browser for performance. This means that the application needs to be
able to generate a file tree identical to the URL structure so that clients can
fetch a single URL and either use the cached image or trigger a manipulation
depending on whether it already exists.
With a url structure of /key and /key/manip for the source and manips respectively,
it becomes impossible to create a file tree matching it since 'key' must be both
the source file and a directory containing the manipulated images.
This updates it to use 'original' as a special manip name so the URL structure of
/key/original and /key/manip can match the directory structure
Abandon all but the simplest of auth schemas
Remove dynamic image generation
Add support for cache control
Add support for 501, 405, and 422 status codes
