Update images from Owncloud to S3 automatically

At the moment there is a manually triggered Python script to update the images.

Differences at S3 to Owncloud are not deleted on S3 at the moment.

Owncloud connection etc. can be reused from Germania Sacra.

Functional account gfl@sub.uni-goettingen.de can be used.

• Credentials are here: https://intranet.sub.uni-goettingen.de/display/prjGFL/Betrieb#Betrieb-Infrastruktur