This adds the initial collection of tests specifically for `limbo`
shell/cli behavior, to separate the concern from testing the underlying
dbms.
Also adds `Echo` mode, and `quiet` mode cli argument for better
experience piping output of limbo on the command line.
After writing a ton of tests in `tcl`, I realized that there is no
reason at all to write these particular tests in tcl anymore, so I
rewrote them in python :)
Shell tests were added to `make test` to run in CI
Closes#487