adds support for rqworker settings files

[prehensile]

as detailed at https://python-rq.org/docs/workers/

Allows rq-scheduler to read from these config files, thus enabling sharing of config with rqworker.

[selwin]

Hi @prehensile , I think this is a great idea. Do you mind if we reuse RQ's implementation for much of the configuration parsing though? I'd rather keep the two scripts as similar as possible for consistency and to lower maintenance burden.

For example, we can delegate connection setup to rq.cli.cli.connect, the cli script also has many decorators that we can reuse to simplify argument parsing such as url_option and config_option.

Ideally, we should also convert the script to use click - this means we should also require a recent version of RQ in setup.py

[prehensile]

@selwin good points, I'll have a look.