Implement job control - Githubissues

TODO

[x] Add unique id to log (to enable log messages to be correlated to the specific shell)
[ ] Fix builtin commands and wait_for_job. If a background job is running and a builtin command is called, waitpid will spin infinitely.
[ ] Support starting commands in background with &
[x] Split integration tests into many tests
[x] Add test for command not found (and prompt regression)
[x] Add test for syntax error handling

rgardner / bsh-rs