This adds the 'wait' subcommand that will allow to wait for
test jobs completion.

It uses polling to check for the job status every 30 seconds
and showing its current status to stdout.

It defaults to a waiting timeout of 10800 secs (3 hrs) but this
can be changed using the '--timeout' flag. The waiting can be
interrupted using Ctrl-C.

The subcommand is also made available as the '--wait' option
in the submit command, so that it can be used while submitting
jobs at once, like for example:

$ lqa submit --all-profiles -g profiles.yaml --wait