Fixes to obsolete file names and wrong version numbering for backups

[susanodd]

Fixes to bak bak old style file names. Fixes a bug in the API that all backups are given version number 1.

• Some of the code is still using (version * ".bak") extensions. That has been changed to the new format .bakNNNN

• The logging has been repaired to only put a deleted video in the history, not all the reverted videos (those are still on the file system)

• The renumbering of older backups has been updated so they get new version numbers

• The retrieval of GlossVideo objects explicitly excludes subclass objects (only the prime videos are versioned)

The branch includes a minimum amount of code to achieve the goal: use the new format for file names.

Old file names can be repaired elsewhere (pull requests in other branches)

[susanodd]

UPDATE @Woseseltops

On signbank-test you can

• Use the Swagger API to upload videos
• To confirm that the version numbers are being incremented (the bug on master/production sets them to 1)
• Use Manage Datasets -> Manage Video Storage to inspect the paths of the gloss video objects

[Woseseltops]

• Nothing to complain about code wise.
• Functionally, I tested as @susanodd describes and can confirm that using the API to upload multiple video files results in backups like this

0: glossvideo/NGT/WE/WEBCAM-2211.mp4, 1: glossvideo/NGT/WE/WEBCAM-2211.mp4.bak24466, 2: glossvideo/NGT/WE/WEBCAM-2211.mp4.bak10152