Use NEAR access keys properly

[Sladuca]

Problem

right now the wallet only stores and manages "root" keys. However, near's account structure is more complicated than that since it allows for having specific keys that can have a certain permission scope. By default, we should use these access keys and use them in a manner as granular as possible. This could mean storing a separate access key for every method on every smart recipient smart contract (which could be a user).

Solution

Make a proposal on how we ought to go forward with access keys and implement it. Would necessarily entail:

• learning how NEAR's access keys are formatted
• learning how and when NEAR's access keys are suggested to be generated
• comparing the previous two with how /signTx is implemented