Allow more generic way for securely storing data

[co-dax]

The current way of securely storing data is implying that the context is around username, password and server but there might exist an arbitrary situation when we need to store some data and while the current approach (just described above) does/can work it is semantically awkward to use it thus a function name like NativeBiometric.setData({key: string, value: string }) would be more applicable for whatever use case. For example, we may want to securely store a pin code and the current interface (server/username/password) would not be the most appropriate (semantically).

[co-dax]

...by the way, by implementing a function like suggested above NativeBiometric.setData({key: string, value: string }) we would essentially be allowed to store even a json object by serializing it to a string using JSON.stringify() function and saving the result as a string by passing it as value parameter to the newly introduced function NativeBiometric.setData({key: string, value: string }) thus allowing us to also have the current server/username/password functionality by using server as a key and a JSON {username: string, password: string} as value in the newly implemented functionNativeBiometric.setData({key: string, value: string })