Rewrite rejester.run using yakonfig.cmd.ArgParseCmd; minor CLI changes.

'rejester mode run', not 'rejester set_RUN'.  This change also means
that running 'rejester' with no command will put you into an interactive
shell, and that commands take parameters ('rejester delete -y', not
'rejester -y delete').

Add a complete test suite covering all CLI commands that doesn't depend
on pexpect.