Import tool for lecture blocks

Creating multiple lecture blocks is a cumbersome task. It is desired to have a simple import to create many lecture blocks at once based on an excel sheet. The import is implemented like the user import with a copy / paste action into a single text area field. 

Example of how the import could look something like the attached excel.

The import should check is such a lecture block already exists and skip it in such a case. If the external ID is provided and the the lecture block already exists it should be updated