Apps for closed data

[dirkroorda]

Central to the TF-App functionality is the auto-download feature.
But this requires the data to be open.

Yet a corpus cannot always be open, e.g. when it contains sensitive data (privacy, commercial interest, copyrighted material).

Also in those cases we want to be able to run the TF browser, which requires a TF app.

So: make the auto-download part optional for TF-apps.

[dirkroorda]

A better way is to allow backends that are closed, e.g. GitLab with closed repositories.
In the meanwhile, this is implemented in Text-Fabric. In order to work with restricted repos on GitLab, you have to provide an API-key, much like the API key for GitHub that you need to increase the rate limit there.