[IDEA] Keys that can only interact with one token type

[Kyrrui]

In the name of security, I think it would be awesome to have keys that are limited to transferring only one type of token on an identity. This way, if a user has an identity and adds a key from this clicker example, that key can only use kilks. This way, even if a key from the clicker service becomes compromised, the other funds in the users identity are guaranteed safe.

[alexvandesande]

This will be possible with authorization contracts: #88

[alexvandesande]

I'm closing this issue, as it's sort of a duplicate of that