Review/Improve method performance

[dominikl]

Some getter methods seem to time out (fail with JDBC exception) when dealing with many objects, see “Could not roll back JDBC transaction”. They are also much slower then using HQL directly. They should be reviewed and improved if possible. It's also worth thinking about adding pagination options.

[imagesc-bot]

This issue has been mentioned on Image.sc Forum. There might be relevant details there:

https://forum.image.sc/t/could-not-roll-back-jdbc-transaction/51774/4