Dallas and I both spent some time working on this. I decided to keep working on ownCloud 5.0.
After configuring External Storage to connect using swift, I also saw a blank page when going to the Files section. I also kept seeing the following error in owncloud.log:
Integrity constraint violation: 1048 Column 'id' cannot be null
Looking at the oc_storages table, there was definitely an id field and it definitely was not null...
So, I abandoned swift and took a different route - I modified ownCloud 5.0 to use S3 and point to DreamObjects. Here's what I did:
Where you do this work depends on where you've installed ownCloud. I installed mine in a directory called owncloud so the work I did was here
Make a backup copy of amazons3.php
After line 41, add the following 2 lines:
Configure an Amazon S3 bucket in the admin settings
As mentioned, it's a hack. It's working well for me in my testing so far. Let me know if you've given this a try!