Make mnemonic cards as plain and simple as possible

[fdegros]

At the moment, the generated mnemonic cards contain lots of information: mnemonic words, group composition, group names, group thresholds, cryptocurrency names, cryptocurrency addresses, watermarks...

As a consequence, they look quite "crowded", and they feature some data that I don't want to disseminate with my mnemonic cards.

I would prefer these cards to be as simple, plain and "boring" as possible. This is a security feature. I don't want these cards to attract any unwanted curiosity or attention. I don't want them to leak more information or hints than necessary. I don't want them to have any reference to cryptocurrencies. And I certainly don't want them to give away the addresses of my wallet, or the cryptocurrencies I'm interested in.