Return uuid when create a new keystore from LocalWallet

[stephenctw]

Currently the LocalWallet::new_keystore() doesn't return the uuid that's available from the inner eth_keystore::new call. Making it impossible to manage the keystore in the filesystem programmatically. Please also return the uuid from eth_keystore::new so the actual keystore file can be located easily.

[gakonst]

@roynalnaruto FYI

[roynalnaruto]

@stephenctw Thanks for having created the issue. I've made the necessary changes in the above linked PR 👍

[gakonst]

@stephenctw closing, please re-open if the PR doesn't address your problem!