Prepare REPOSE app for incoming passphrase

This only concerns the app version for the REPOSE study.

Study participants receive a respondent ID + a passphrase that is used to encrypt the data (as a zip archive) before transmitting it to the Charité server. These two strings need to be handled by the app and saved to the settings.

I created a new module ReposeDataModule that takes care of this. I included example data; in reality this will happen through a QR code, but that is part of another issue.

The following data structure was proposed by Andreas:

{ repose: { respondent-id: '0123', passphrase: 'sedrtz8u657zf' } }

I created a settings group and saved the ID and passphrase as two separate entries within that group.

It would be nice to have copy for this, I just came up with translations on the fly. Terminology is also still subject to change (I'm considering changing respondent-id to pseudonym).