Transkribus import needs a worker version

Quick fix is to provide a specific Worker version id from the backend directly to the task.

1. Create a script that produce a fake repo/revision/worker/workerversion for Transkribus
2. Add that specific version in the payload task as an environment variable when starting an import
3. Use the env variable in the transkribus import task, for all CreateXXX api calls, especially in save_element_transcriptions