Support for password protected private keys

[heartsucker]

No description provided.

[cavokz]

Is there anything that can be reused from other crates or that makes sense to contribute to them? Just to avoid reinventing the wheel or, if we do, share it with others before they reinvent it on their own.

[heartsucker]

I can't remember what my original intention of this was, but I think it had to do with storing private keys on disk which for use with the CLI I was working on. I scraped that at some point to focus on the core lib, and this kinda makes protecting the keys out of scope (for now).