Excel import of processes: multiple processes with the same UUID can be created

[msrocka]

Problem: Create a process in openLCA -> export it with the Excel export -> modify it in Excel and import it into the same database -> there are now two processes with the same UUID in the database

The user should be able to decide whether to keep the existing process in the database or to replace it with the version from the Excel file. Therefore, we need some kind of user interface. However, it gets complicated when a process should be replaced that is already used in a product system as the old links may not valid anymore with the new version (when the product or waste flows changed in the process). An option would be to not allow to replace such a process in this case showing a message like A process that is already used in a product system cannot be replaced.