Revert "Create 'latest' file in root of artifacts"

This reverts commit 2242334aae2aa7b5d34f62b0cad973de5ada409b.
Build uses UploadAdapter to upload gems
Removed PipelineStorage
download adapter can also take a string URL
download adapter returns the absolute path of the downloaded file
add an automated bosh deployer for ci promotion
Reduce public interface around promoting artifacts
Inlining private method #create
Removed unused public method #fog_storage