Issues with first run of notebooker

Hi,

I have tried to go through the install explained there:
https://notebooker.readthedocs.io/en/latest/setup.html#first-run-of-notebooker

I have mongodb running, but when I try to access the app, I get an error
`Internal Server Error
The server encountered an internal error and was unable to complete your request. Either the server is overloaded or there is an error in the application.`

and can see in the logs:
`KeyError: 'notebook_templates_example'`

In mongodb, the notebooker database and the NOTEBOOK_OUTPUT_scheduler collection has been well created.

Thanks

Start with the first-run instructions at setup.html#first-run-of-notebooker and reproduce the app access failure with MongoDB running. Trace the KeyError: 'notebook_templates_example' from the application logs and compare it with the created notebooker database and NOTEBOOK_OUTPUT_scheduler collection. Done means the first run completes without the internal server error.

Written by the indexing model from the issue text.