Multi-key import feature

[leviathanbeak]

Summary of changes
Changes introduced in this pull request:

• instead of reading the key from the command argument, we either read the path to the key, or if there is no path provided we read it from stdin (the same way lotus does it)

Reference issue to close (if applicable)
Closes #1129

Other information and links

[cryptoquick]

I really like it! Thanks so much for your continued involvement on the project.

I left a couple nits, but while you're at it, do you think you could make it so this error returns a code other than 0?

Do you think you could also make these work? I'm a little rusty with my bash shell, but I think this is how you do this, right?

Key import from path doesn't seem to decode correctly? Or maybe it's string trim, not sure. Either way, it doesn't work.

From a user experience standpoint, I think we should also make it also print out the key on a successful import so the user knows which key they just imported. Right now no message is returned other than exit code 0.

Also, do you think you could make it trim the string input? If you accidentally add extra space to stdin when copy/pasting, that might be nice.

In summary:

• Fix qualified std import nit
• Make key import work with stdin in addition to read_password (if possible)
• Fix path import decoding issue
• Fix "key already exists" error code so returns other than 0
• Print out key name after succesful import
• Trim string input

I know it's a lot more work than originally specified, but that'd really help us out. That's whole point, right? And thanks again for your contributions so far!

[leviathanbeak]

@cryptoquick thanks for the detailed review, I didn't expect it to be that easy anyway, will improve it

[cryptoquick]

Haha, great!

[leviathanbeak]

In summary:

• Fix qualified std import nit
• Make key import work with stdin in addition to read_password (if possible)

fixed this by only updating rpassword lib, it was very, very outdated

• Fix path import decoding issue

added trimming - should fix all the problems

• Fix "key already exists" error code so returns other than 0

as discussed, the problem was in 2 places, fixed it

• Print out key name after succesful import

added println!(key)

• Trim string input

[cryptoquick]

Good catch on the outdated rpassword crate! Just tried it out, it all works great. Thank you so much for your solid contributions!

Also, as mentioned in #fil-forest-dev in the Slack, we decided the error code change isn't needed for this PR.