Keystore API

[thiagodelgado111]

A few questions about keystore's API:

• Are all the methods available being used? Some of them seem redundant when we have getKey? e.g: importPublicKey and importPrivateKey (Maybe I didn't get how they're being used or where. I saw that the former is used by ipfs-log it seems)

• Should it be responsible for generating / creating keys or just loading it? Currently, we are creating a new key every time a key isn't found at the keystore storage maybe that should be explicit so we don't end up doing that accidentally. Also, for cases where we don't wanna store the key on local storage or leveldb, we could keep generateKey and make it return a key-pair.

• Suggestion: Can we give the keystore both a key and a signer object via constructor?
  Why: For a dApp you most probably already have a key and a wallet you can use to sign messages.