Add “split this collection” button at collection level

[KatharineV]

We prefer to use the UV, but we had to turn it off so we could very quickly ingest the remaining works from our Islandora migration. Rather than rely on SoftServ to manually resplit the thousands of works that need to be split for the UV, we suggest that a "split this collection" button be put at the collection level, if that's not too big of a lift. This way, we could split sets of works without requiring SoftServ time. Additionally, we spoke with some other Hyku users who agree this would be a useful feature for Hyku in general, so it could be a great feature to contribute back.