keybase command line client should know about my existing GPG keychain

I already have some people who I exchanged keys with before. They are listed in my trust DB and I signed their keys. The cmd client should import these connections automatically.

Start by locating the command-line client entry point and documenting how it currently discovers or imports keys; no files or tests are named in the issue. Done means the client can account for people already present in the user's GPG trust database and signed keychain, with behavior and compatibility expectations clarified.

Written by the indexing model from the issue text.