Please add cl-progress-bar

[sirherrbatka]

cl-progress-bar contains code blantly stolen from quicklisp client, sligthly altered for more general use case (thread safety, ignore nested requests to create progress bar, be able to disable and enable progress bars printing).

Author: Marek Kochanowicz
Repository: https://github.com/sirherrbatka/cl-progress-bar

[quicklisp]

Please add a description to the system definition.

[sirherrbatka]

Done.