Give option to generate wallet password

[angaz]

Closes #248

As pointed out in the issue, and from my understanding, the password is not used for any purpose other than during wallet init, and wallet restore, so giving the user an automatic way to generate the password would be nice.

I've added the functionality in a way that is least intrusive to the current flow, but I see no reason to prompt the user at all for the password. So if we want to remove the prompt completely, I will update the PR with that.