Add support for loyalty cards

**Is your feature request related to a problem? Please describe.**
Now I use [Catima](https://github.com/CatimaLoyalty/Android) and KeePassDX at the same time and it's annoying because I have to juggle with two vaults/databases. The common thing between both of these is that them are about secrets/tokens and only the presentation differs. Passwords is just secrets that are used as such, TOTP seeds are secrets that is used through a generator and loyalty cards are secrets that is used in the form of a QR code or barcode. Just simple string name-value pairs.

**Describe the solution you'd like**
Default form for loyalty card and QR and Code 128 barcode generator.

Review how the vault represents password and TOTP secrets, then identify where a default loyalty-card form and QR or Code 128 presentation would fit. Clarify the name-value fields and supported barcode behavior before implementation; done means loyalty cards can be stored and displayed in the requested formats.

Written by the indexing model from the issue text.