DRAFT: Offline money app

[Robert-ML]

Offline money application.

At the moment it contains the ability to exchange token based currency through the scanning of a QR code. This means it is completely offline. The printing of money is done in demo mode using a pre-shared private-public key. The app has data persistency.

TODOs:

• BUG: when removing tokens from the persistency DB, the removal is not happening;
• do security check when transactioning tokens
• do security check if token is signed by pre-shared public key representing a central authority
• detect double spending and the culprit

[Robert-ML]

Can somebody put the lable "draft" on this PR?