Rev full asset directory 

I have a directory with localization files. The filename is used to select the correct file for a locale, so it should remain the same. Instead the directory name can be changed in a similar manner, so:

  dir/file-en.json -> dir.a2aa178/file-en.json
  dir/file-nl.json -> dir.a2aa178/file-nl.json

the hash is based on the full contents of the directory.