fork/copy from previous version with source and translation

http://bugzilla.redhat.com/show_bug.cgi?id=1104015
I discussed this in person, but will add a comment here for posterity.

Raw files are stored in the file system after they have finished uploading and processing, but they will be overwritten if a new version is uploaded, so they should be duplicated when the document is duplicated so that there is no potential interaction between documents in different versions.

During upload, raw files can be stored as chunks, which I believe are still Blobs in the database. These last until the upload is finished, then they are combined into a file, hash-checked and processed. Since these chunks are not long-lived, and it does not make sense to upload half a file to one version and the other half to another, they should not be copied to a new version.

In short:

 - HRawDocument should be duplicated to new version
   - associated file on file system should be duplicated as well (copy bytes)
 - HDocumentUpload and associated entities should not be duplicated to new version