Revert "Bump Paperclip to 4.1.1"

This reverts commit e867cf0ceada045e477f60d92f1fb0ef3d163f80.
Revert "Need to pass through a content-type when using upload_image to appease paperclip"

This reverts commit b04d57cd7ed194fcf59c4ed67e844c832bdbcc2d.
Fixes #4304 - RABL cache collision for variants

This uses string prefixes within each variant template to ensure unique cache keys and guarantees no collisions.

Fixes #4308