Sample batch importer ignore parent used quantity

[Nicklas Nordborg]

Use the "Sample batch importer" to import child samples to already existing samples in the database. The existing samples should have values for the "Original quantity".

The import configuration should specify a "Parent" item (sample) and a "Parent used quantity".

The child and parent items are linked correctly, but the remaining quantity of the parent is not affected.

The only workaround is to manually update the used quantity with the web interface.

[Nicklas Nordborg]

(In [5988]) Fixes #1665: Sample batch importer ignore parent used quantity

There was also a problem with "updating" to the same parent item. Eg. calling BioMaterialEvent.setParent() with an item that was already a parent. This caused a duplicate key violation in the database since the code created a new link, before removing the old one. The updated code re-uses the existing link to avoid the problem.