feat(importers): add copyRecords tool for importing individual records

[andersju]

Something I've wanted for a long time but couldn't be bothered with until now.

To import sample records to a dev db we've only had the importer tool's copywhelk command, which takes a file with a list of IDs (and optionally a list of types to copy). This is mainly intended for the initial run when (re)creating a dev db. copywhelk redenormalizes the entire db and doesn't reindex on its own.

The use case this PR solves is: "I have an existing dev database and I just want to quickly import one or a few specific records and their dependencies/dependers from the prod db (and redenormalize+index only what's necessary)". Et voilà:

cd importers/
../gradlew jar

To import a couple of records by short ID, including their version history and holdings (if any):
java -Dxl.secret.properties=../secret.properties -jar build/libs/xlimporter.jar copyRecords --copy-versions --include-items ../temp_source_secret.properties 4ngh2qhg49jhnp4 vhsxx8rks82lgtn5

By IRI:
java -Dxl.secret.properties=../secret.properties -jar build/libs/xlimporter.jar copyRecords --copy-versions --include-items ../temp_source_secret.properties https://libris.kb.se/4ngh2qhg49jhnp4

Where temp_source_secret.properties contains the details for the source database (e.g. qa/stg/prod readonly...). Just like with copywhelk.

--overwrite-existing can also be specified. In that case the specified record will be updated with the contents of the source version (but then version history is not copied).

[kaipoykio]

Looks fine!