Check and incorporate LOCKSS patches for v4

[poikilotherm]

@lockss made a few patches in their fork:

• https://github.com/lockss/lockss-fork-dspace-xoai/tree/release-4.1.0-p4
• https://github.com/lockss/lockss-fork-dspace-xoai/tree/develop-xoai-4.1.0
• https://github.com/lockss/lockss-fork-dspace-xoai/tree/develop-xoai-4.2.0

Analyse and maybe incorporate them.

It looks like there is a single commit with all their relevant changes to look at for us:
https://github.com/lockss/lockss-fork-dspace-xoai/commit/c87c5219f910334212e4ff01d2f189ea33c7ee00

• They implemented retries for the ListRecordHandler (which Dataverse doesn't use - we provide our own implementation)
• They added sth. that looks like a fix for handling Dublin Core dates in the metadata parser

[poikilotherm]

These changes are about the service provider, which Dataverse does not use at all. Skipping for now. Might be taken up again at a later time #17 and others