Create new `kr` complement to `kp`

[matthewwardrop]

As a rough idea, something like:

• [ ] Add new script kr for interacting with knowledge repositories, and adding/managing knowledge posts therein.
  • [ ] kr [--repo <repository (alias? defaulted?)>]* add <post_path> [--path <kr_path>] [--update]
  • [ ] ~kr [--repo <repository (alias? defaulted?)>]* submit <kr_path>~ [Adding to a knowledge repo is submission with these tools.]
  • [ ] kr [--repo <repository (alias? defaulted?)>]* get <kr_path> [--path <local_path>] [--format <format>]
  • [ ] kr [--repo <repository (alias? defaulted?)>]* serve ...