Distinct endpoint handler for binaries/images uploads

[clemensv]

I'd like editors embedded in the site like TinyMCE to be able to upload images directly using a distinct endpoint rather than having to use a secret-handshake form parameter (submit="Image Upload") in the edit handler.

Ref: https://www.tiny.cloud/docs/general-configuration-guide/upload-images/

[poppastring]

Working on this issue.