Improve usability of orly console.

Make `orly_client` be a nicer interpreter. Common `bash` key combinations work, such as,
* `Up-Arrow` to go up history.
* `Ctrl-R` for reverse-history-search.
* `Ctrl-C` to abort the current line
* `Ctrl-D` on an empty line to exit.
* `Ctrl-L` to clear.

Type `help` or `?` to get examples of all possible statements.
`Tab` to auto-completes commands.