Document service with Commons VFS

I implement a service class to handle documents in the application
document directory using Apache Commons VFS.  I also implement a list
action in DocumentController which uses this service.
Use only one stylesheet per page

I optimize the dependency calculation for stylesheet files in the asset
pipeline by specifying only one stylesheet per page using the <meta
name="stylesheet" content="..." /> tag.  If the tag is not specified,
the default stylesheet "application" is loaded.